CLAY  PLANT  CONSTRUCTION 
AND  OPERATION 


BY 
A.  F.  GREAVES-WALKER 

CERAMIC    ENGINEER 

Member,  American  Ceramic  Society , 

English  Ceramic  Society,  Royal 

Society  of  Arts,  and  Fellow 

Utah  Academy  of  Science. 


ILLUSTRATED 


BRICK    AND    CLAY  RECORD 

610  FEDERAL  ST.—CHICAGO,  U.  S.  A. 
1919 


Copyright  1919 
BRICK  AND  CLAY  RECORD 


DEDICATED  TO  M.  A.  G.-VV. 


4  f 2Go3 


PREFACE 

E  PROBLEMS  confronting  the  clay  products  indus- 
try  are  naturally  so  numerous  that  an  ordinary  volume 
can  only  deal  with  a  few  of  the  larger  ones.  There  can  be 
no  question  whatever  but  that  the  industry  as  a  whole  faces 
more  difficulties  than  any  other,  yet  up  to  ten  or  fifteen 
years  ago  practically  no  scientific  effort  had  been  made  to 
solve  the  greater  portion  of  them. 

As  a  manufacturing  industry  it  has  been  also  probably 
the  most  wasteful — wasteful  of  human,  mental  and  finan- 
cial effort.  Only  recently  has  economy,  scientific  economy 
been  practiced  by  an  appreciable  part  of  the  industry,  and 
still  greater  efforts  must  be  made  in  this  direction  if  it  is  to 
compare  with  many  other  American  industries,  especially 
those  with  which  it  is  in  competition. 

The  entrance  of  the  engineer  into  the  industry  is  begin- 
ning to  make  itself  felt  and  as  confidence  in  his  ability  to 
help  the  clayworker  in  a  practical  way  increases,  far  greater 
benefits  will  be  derived.  One  of  the  greatest  difficulties  en- 
countered heretofore  by  the  engineer  has  been  that  he  has 
only  been  called  upon  to  "doctor"  a  "sick"  plant,  whereas 
he  functions  best  when  acting  in  a  preventive  capacity. 
On  the  other  hand,  ceramic  engineers  must  realize  that  in 
order  to  do  the  industry  and  themselves  the  greatest  amount 
of  good  a  great  deal  of  common  sense  must  be  mixed  with 
their  technical  knowledge. 

In  writing  the  following  chapters  the  author  has  attempt- 
ed to  explain  in  understandable  English  some  of  the  prob- 
lems of  the  manufacturer  of  structural  clay  products. 
Every  effort  has  been  made  to  avoid  technical  terms  and 
formulae.  Theories  have  also  been  avoided  and  plain  prac- 
tical facts  presented.  The  author  has  tried  to  realize  that 
it  is  not  the  ceramic  engineer  or  the  company  employing 
him  that  requires  assistance  but  the  man  who  is  trying 
to  solve  his  own  problems. 


VI  Preface 

It  is  quite  probable  that  some  of  the  statements  made 
will  be  criticised  by  both  technical  and  practical  men.  To 
these  it  would  be  well  to  say  that  no  attempt  has  been  made 
to  treat  individual  problems  and  that  in  order  to  receive 
help  from  this  little  volume  the  clay-worker  must  combine 
with  it  the  experience  he  has  received  in  the  "School  of 
Hard  Knocks." 

New   York    City,    May   15,   1919.  A.    F.    G.-W. 


TABLE  OF  CONTENTS 

CHAPTER  I. 

TESTING  CLAY  PROPERTIES 

Topography— Geology  —  Ware  Manufactured— Market 
—Water  Supply— Sampling— Drilling— Testing....  1-15 

CHAPTER  II. 
HOLLOW  WARE  DIES 

Origination  of  Die  Troubles— Effect  of  Speed  of  Ma- 
chine—Type of  Dies— Taper— Raw  Material 16-26 

CHAPTER  III. 
FACTORS  IMPORTANT  TO  DIES 

Types  of  Auger — Metal  for  Auger — Distance  of  Auger 
from  Die— Force  Feed— Distribution  of  Metal  Back 
of  Dies — Scorers  and  Scratchers — Metal  Baffles — • 
Bridge  Crowns— Die  Ware— Tool  Steel  Die 27-39 

CHAPTER  IV. 

DRYER  DETAILS 

Choice  of  Dryer— Open  Air  Dryers— Dryer  Racks- 
Dryer  Walls— Drainage  40-47 

CHAPTER  V. 
DRYER  CONSTRUCTION 

Rails — Tunnel  Dimensions — Doors — Stack  Construc- 
tion— Storage  and  Cooling  Tracks 48-60 

CHAPTER  VI. 
SETTING  UP-DRAFT  KILNS 

Tight-bolt   Setting— Facilitating  Handling  of  Brick 01-64 

VII 


VIII  Table  of  Contents 

CHAPTER  VII. 
SETTING  DOWN-DRAFT  KILNS 

Effect  of  Setting  on  Burning — Effect  of  Setting  on 
Production — Skilled  Labor — Height  of  Setting — Pre- 
venting Sagging— Laying  out  Runners— Method  of 
Setting  —  Unflashed  Face  Brick  Setting  — Flashed 
Face  Brick  Setting 65-78 

CHAPTER  VIII. 
DOWN-DRAFT  KILN  DESIGN 

Length  of  Burning  Period — Drainage — Foundations — 
Height  of  Stack — Dampers — Walls  and  Crowns — 
Efficiency — Insulation  79-94 

CHAPTER  IX. 
DOWN-DRAFT  KILN  CONSTRUCTION 

Bracing— Steel  Shell  Kiln  —  Crown  —  Furnaces  —  Bag 
Walls 95_io;i 

CHAPTER  X. 
CONTINUOUS  KILN  FOUNDATIONS 

Care  Required  —  Necessity  of  Good  Foundations — 
Drainage  104-111 

CHAPTER  XI. 
CONTINUOUS  KILN  WALLS 

Side  Wall  Construction— Fire  Brick  Lining— Bracing 
Walls— Solid  Brick  Construction— Insulated  Wall- 
Battered  Walls  112-124 

CHAPTER  XII. 
PARTITION  AND  FLUE  WALLS 

Gaf;  Tight  Joint — Flue  Construction — Brick  Gas  Flue — 
Watersmoking  Flues — Expansion  Rollers — Up-Takes 
— Expansion  Joints — Crown — Brick  Arches....  ....125-140 


Table  of  Contents  IX 

CHAPTER  XIII. 

KILN    ROOF   AND    PRODUCER   HOUSE   CONSTRUC- 
TION 

Fan— Roof  Construction— Hip  Roof— Blast  Pipe  Con- 
nections— Size  of  Producer 141-150 

CHAPTER  XIV. 
OPERATING  A  COAL-FIRED  CONTINUOUS  KILN 

Fuel  Requirements — Bracing  Flue  Setting — Type  of 
Continuous  Kiln — Paper  Partitions — Watersmoking 
—Backing  Heat— Wicket  Fires— Draft— Unloading....l5 1-164 

CHAPTER  XV. 
OPERATING  A  GAS-FIRED  CHAMBER  KILN 

Gas  Manufacture  —  Distribution  of  Fuel  —  Rate  of 
Feeding  Producer — Pressure  at  Blower — Cleaning  a 
Producer  —  Setting  —  Watersmoking  —  Burning  — 
Chambers  on  Fire— Flashed  Ware 165-181 

CHAPTER  XVI. 
SUGGESTIONS  ON  PLANT  LOCATION  AND  DESIGN 

Ware  Produced  —  Capacity  —  Choice  of  Equipment — 
Storage — Dryer — Burning  .System — Lay-Out — Power 
— Construction  182-188 

CHAPTER  XVII. 
CARING  FOR  EQUIPMENT 

Machinery — Labor — Repair  Parts — Shale  Pit — Incline 
—Storage  Shed— Power  Plant— Motors 189-198 

CHAPTER  XVIII. 
RUNNING  A  PLANT  TO  CAPACITY 

Dry  Pan — Elevators — Brick  Machine — Cutting  Table — 
Key  Troubles— Belt  Troubles— Dryer— Kilns— Plant 
Inspection : 199-208 


LIST  OF  ILLUSTRATIONS 


FIGURE  PAGE 

1.  Section  of  hill  showing  weathered  material 4 

2.  Section  of  hill  showing  land-slide 5 

3.  Section  of  hill  showing  over-burden 7 

4.  Section  of  hill  containing  worthless  material 8 

5.  River  deposit  9 

6.  Section  of  hill  showing  flint  clay 11 

7.  Lay-out  of  property  for  drilling 14 

8.  Tapered  and  flat  die 21 

9.  Maximum   speed   taper 22 

10.  Spreaders  for  dies 23 

11.  Section  of  auger  flash 29 

12.  Method  of  correcting  fast  flow 32 

13.  Method  of  balancing  die 33 

14.  Balanced  and  unbalanced  die 34 

15.  Adjustable  tool  steel  scorer 35 

16.  Illustrating  method  of  balancing 36 

17.  Serrated  bridge  to  prevent  cracks 37 

18.  Dryer  car  with  weather  protector 42 

19.  Dryer  wall  with  air  space  and  plaster 44 

20.  Dryer  roof   design 49 

21.  Cast  iron  rail  clamp 50 

22.  Single  and  double  tunnel  construction 52 

23.  Double   steel   doors 54 

24.  Steel   lifting  doors 55 

25.  Brick   dryer   stack 56,  57 

26.  Post  for  dryer  shed 59 

27.  Arch   building   and   platting 62 

28.  Tight   bolt   setting 63 

29.  Method  of  raising  heads 65 

30.  Plan  of  herring  bone  skintle  course 66 

31.  Front  elevation,  single  header  and  stretcher.— 67 

32.  Section   thru   bench 67 

33.  Front  elevation  at  tight  bolt  setting 69 

34.  Section  thru  bench  of  tight  bolt  setting 69 

35.  Types  of  setting 70 

36.  Method  of  protecting  heads  from  flashing 71 

X 


List  of  Illustrations  XI 

FIGURE  PAGE 

37.  Setting  kiln   on   flat 72 

38.  View  of  kiln  on  flat  setting 74 

39.  Plan  views  of  settings  in  Fig.  38 75 

40.  Tight   bolt  flat   setting 76 

41.  Combination  flat  and  edge  setting 77 

42.  Thirty-foot  round  kiln 82 

43.  Bottom  for  thirty-foot  round  kiln 84 

44.  Rectangular  kiln  85 

45.  Bottom  for  rectangular  kiln 86 

46.  Two-stack   kiln   89 

47.  Thirty-foot  kiln  sweep 99 

48.  Fire  boxes 102 

49.  Wrong  construction  of  kiln  foundation 106 

50.  Correct  construction  of  kiln  foundation 107 

51.  Construction  of  waterproof  bottom 108 

52.  Construction  of  waterproof  bottom 109 

53.  Hillside  wall  for  drainage  protection 110 

54.  Section   of  wall 115 

55.  Door   construction   116 

56.  Section  of  solid  wall „ 117 

57.  Section  thru  inside  wall 118 

58.  Location  of  expansion  joints 119 

59.  Section  of  straight  wall  and  iron  work 121 

60.  End  batter  wall  and  cross-over  flue 122 

61.  Tongue  and  groove  shapes 126 

62.  Bag   wall   127 

63.  Gas  distributing  flue  and  down-take 128 

64.  Lining  gas  flue 129 

65.  Expansion  at  flue  elbows 131 

66.  Care  of  expansion  at  flue  elbows 132 

C7.     Elbow  of  brick  flue 133 

68.     Flue  wall  construction 135 

S9.     Crown  showing  expansion  joint 139 

70.  Producer   house   144,  145 

71.  Soot  chambers 147 

72.  Setting  race  flue 153 

73.  Setting  fire  shafts 155 

74.  Diagram  of  advancing  heat  in  producer  gas  kiln. ...173 

75.  Starting  gas  kiln  on  fire 178 

76.  Showing  burning  circuit  of  gas  kiln 179 

77.  Cage  for  haulage  system 195 

78.  Step   protector  200 

79.  Clay  plant  elevator 202,  203 


Clay  Plant  Construe 
tion  and  Operation 


CHAPTER  I 


Testing  Clay  Properties 


MANY  CLAVWORKERS  the  above  subject  will 
seem  so  elementary  as  to  be  almost,  if  not  quite,  above 
notice.  That  many  prospective  and  actual  clay  plant  owners, 
to  say  nothing  of  the  army  of  farmers  and  promoters  who 
have  dabbled  in  clay,  have  so  regarded  the  subject,  is  very 
evident  from  the  vast  number  of  "dead"  clay  products 
factories  which  dot  the  country. 

The  outsider  is  not  to  be  greatly  blamed  for  overlook- 
ing or  utterly  ignoring  the  necessity  for  a  thoro  testing 
of  a  property  but,  for  the  clayworker,  there  is  absolutely 
n -j  excuse,  for  he,  of  all  others,  knows  the  treacherous 
nature  of  his  raw  material.  He  has  in  many  cases,  how- 
ever, handled  the  matter  as  he  has  handled  his  plant 
design,  equipment  and  kiln  construction — with  his  eyes  and 
cars  shut. 

In  looking  about,  it  is  really  surprising  to  note  the 
immense  waste  of  money  due  directly  to  the  erection 
of  plants  without  first  making  the  proper  tests  of  the 
raw  material  it  was  proposed  to  use.  A  few  instances 
will  be  of  interest. 

SPENT     $250,000     ON     STRENGTH     OF     SURFACE     SAMPLES 

A  clay  products  company  which  had  been  in  successful 
operation  for  twenty  years  found  it  advisable  to  sell  its 
plant  site  and  clay  pit  because  of  its  value  as  real  estate 

1 


Plant  Construction  and  Operation 

thru  the  growth  of  the  adjacent  city.  With  well  on  to  a 
half  million  dollars  in  cash  to  its  credit  it  sought  another 
site  in  the  vicinity.  The  manager  and  superintendent 
selected  a  promising  piece  of  land  within  ten  miles  of 
the  old  plant  which  appeared  to  them  to  be  in  the  same 
geological  formation.  A  few  surface  samples  were  taken 
and  made  up  at  the  old  plant  and  these  samples  appeared 
to  be  all  right.  Without  any  further  tests,  a  quarter  of  a 
million  dollars  was  spent  in  erecting  a  factory. 

As  soon  as  the  plant  commenced  operations  it  was  found 
that  the  entire  property  was  covered  with  a  blanket  of  from 
two  to  six  feet  of  the  clay  which  had  been  tested,  while  be- 
neath this  was  an  entirely  different  clay.  This  latter  deposit, 
while  workable,  would  not  dry  safely  under  any  circum- 
stances. 

The  company  has  been  experimenting  for  three  or  four 
years  in  an  endeavor  to  use  the  material  and,  in  so  doing 
has  used  up  its  cash  balance,  mortgaged  the  plant  and,  worst 
of  all,  has  lost  a  splendid  business  to  its  competitors. 

The  testing  of  this  property — which  was  clay,  not  shale — 
would  have  been  extremely  simple.  A  hand  auger  would 
have  divulged  the  useless  material  in  the  first  hole  sunk. 
Further  than  this,  an  appeal  to  the  officials  of  the  govern- 
ment geological  department  for  information  would  have 
warned  them  off,  for  the  geologists  were  thoroly  familiar 
with  the  characteristics  of  this  clay  bed. 

BUILT  NEW  PLANT  WITHOUT  ANY  TEST  WHATEVER 

Another  instance  worthy  of  mention  is  that  of  a  clay- 
worker  with  years  of  experience  who  sold  his  plant  and  de- 
cided to  erect  another  on  a  piece  of  property  he  had  re- 
tained about  a  quarter  of  a  mile  from  his  old  plant.  With- 
out any  tests  whatever,  the  plant  was  laid  out  and  erected. 
The  idea  was  to  get  the  raw  material  from  a  hill  at  the  rear 
of  the  factory,  but  it  was  soon  found  that  this  entire  hill 
was  covered  with  a  glacial  drift  which  was  literally  full  of 
lime  pebbles.  Further  tests  showed  that  the  plant  itself 
had  been  erected  upon  the  very  best  of  the  deposit  and  that 
that  part  of  the  flat  land  which  had  no  buildings  upon  it 
had  apparently  been  cut  thru  by  an  immense  river  or  glacier 
and  then  filled  with  quicksand.  The  result  was  that  the 
clayworker  in  question  lost  his  interest  in  the  company  and 
is  apparc-ntly  out  of  the  game  for  all  time. 


Testing  Clay  Properties  3 

PROFITED   NOTHING  FROM   COSTLY  EXPERIENCE 

A  third  instance  is  rather  interesting  because,  in  this  case, 
the  company  involved  owns  a  number  of  plants  and  had  pre- 
viously lost  one  soon  after  purchase  thru  the  absolute  dis- 
appearance of  the  shale  deposit,  this  being  replaced  by  a 
useless,  stony  clay.  It  would  be  expected  that  one  such 
experience  would  make  a  company  move  cautiously,  but  this 
was  not  the  case. 

At  one  of  the  plants  the  shale  became  so  hard  as  to  be 
almost  unworkable.  It  was  therefore  decided  to  move  to 
another  hill  close  by  and  there  open  a  new  pit.  An  expen- 
sive incline  and  tramway  were  installed  and  the  pit  opened. 
The  first  shale  taken  from  the  new  opening  was  so  high 
in  lime  as  to  be  useless.  After  working  thru  a  pretty  thick 
deposit  of  this  class  of  material,  the  shale  become  as  hard 
as  that  in  the  old  pit.  The  consequence  was  that  after  a 
large  expenditure  of  money,  the  demoralization  of  a  good 
organization  and  quite  a  long  shutdown,  the  new  opening 
was  abandoned. 

PECULIAR    DEPOSIT    FOOLED    FIRE-BRICK   CONCERN 

It  is  a  pretty  well-known  fact  among  ceramists  and  geol- 
ogists that  flint  fire-clay  occurs  in  lens-shaped  deposits  and 
that  some  of  these,  especially  in  the  West,  are  quite  small 
and  irregular  in  distribution.  Upon  the  discovery  of  one 
of  these  deposits,  a  company  was  organized  to  build  a  re- 
fractories plant.  As  it  happened,  the  original  deposit  only 
contained  a  few  hundred  tons  and,  altho  the  property  was 
thoroly  searched  for  a  furthef  supply,  none  was  found  of 
sufficient  refractoriness  to  meet  the  requirements.  The  plant 
was  finally  equipped  to  turn  out  other  clay  products,  but  not 
until  after  the  original  investors  had  lost  the  money  they 
put  into  it. 

"BIG   MONEY"   MAKES  BAD   MISTAKE 

The  promotions  which  have  gone  the  road  to  ruin  thru 
not  properly  testing  the  properties  are  innumerable.  One  of 
these  instances,  which  was  notable  because  of  its  size  and 
the  fact  that  the  project  was  floated  in  one  of  the  largest 
of  the  country's  financial  centers,  is  worth  mention. 

The  plant  was  completed  and  operations  commenced.  It 
was  then  found  that  the  ware  could  not  be  safely  dried. 
Some  of  the  best  expert  advice  in  the  country  was  obtained, 


4         Clay  Plant  Construction  and  Operation 

without  results.  Finally  a  railroad  twenty-five  miles  long 
was  built  to  a  workable  deposit,  but  it  was  soon  found  that 
the  cost  barred  the  products  of  the  factory  from  the  market. 


Fig.    1.    Section    Thru    Hill    Showing   Weathered    Material   on 
the   Surface. 

The  plant  was  soon  abandoned  and  today  the  investors  un- 
doubtedly class  clay  products  with  salted  mines  and  "wild 
cats"  of  all  descriptions. 

Enough  of  such  cases  could  be  recounted  to  fill  a  book, 
but  the  above  will  serve  to  show  in  a  small  measure  how 
this  very  important  problem  is  so  often  approached,  even  by 
those  with  years  of  experience  behind  them.  It  is  small 
wonder,  under  these  conditions,  that  the  bankers  of  the 
country  look  upon  the  clayworking  industry  as  one  of  the 
greatest  risks  with  which  they  have  to  deal. 

In  the  selection  of  a  clay  property  many  items  must  be 
considered.  Among  these  is  the  topography,  geology  of 
the  district,  ware  to  be  manufactured,  location  with  regard 
to  market,  shipping-  facilities  and  water  supply.  These 
items  bear  a  close  relation  to  each  other  and  must  be  con- 
sidered as  a  whole  rather  than  separately. 


TOPOGRAPHY 

It  is  generally  recognized  that  it  is  better  to  win  material 
from  a  hillside  than  to  have  to  go  below  grade   for  it.     In 


Testing  Clay  Properties  5 

selecting  a  hillside  in  which  to  open  a  clay  or  shale  bank 
there  is  the  great  advantage  of  using  gravity  in  moving  the 
mined  material  to  the  factory.  There  is  also  the  advantage 
of  drainage  and  big  working  faces  which  makes  for  eco- 
nomical shooting  or  steam  shovel  operations.  These  items 
count  heavily  in  the  cost,  especially  where  sharp  competi- 
tion is  to  be  met.  It  would  not  be  wise  for  a  company  to 
select  a  site  where  it  was  necessary  to  open  a  pit  below 
grade  or  a  room  and  entry  mine,  if  its  nearby  competitors 
had  a  hillside  bank  with  its  accompanying  lower  costs,  un- 
less there  were  other  conditions  directly  connected  with  the 
mining  operation  which  counter-balanced  the  first  mentioned 
advantage.  More  modern  equipment  in  pit  and  factory 
could  not  be  relied  upon  to  offset  this  point  in  his  favor,  for 
the  competitor  could  modernize  his  equipment  and  still 
maintain  the  lead. 

If,  on  the  other  hand,  a  site  is  selected  which  puts  the 
company  on  an  equal  footing  with  its  competitors  or  better 
still,  gives  it  advantages,  there  can  be  no  fear  from  this 
source  under  proper  management. 

GEOLOGY 

A  geological  knowledge  of  the  district  containing  the  de- 


Fig.   2.      Section    of    Hill    Showing    How    Landslide    Changes 
Surface   Indications. 

posit  is  valuable  and  important.  It  loses  some  of  its  im- 
portance after  the  property  under  consideration  has  been 
thoroly  tested,  but  in  many  cases  it  is  still  important.  In  the 


6         Clay  Plant  Construction  and,  Operation 

fire  clay  areas,  glacial  areas  and  in  districts  where  the  strati- 
fication has  been  much  disturbed,  it  is  an  item  which  must 
not  be  overlooked. 

A  company  may  test  out  an  area  that  looks  in  the  begin- 
ning as  tho  it  were  inexhaustible  only  to  find  out,  in  later 
years,  that  it  must  open  up  on  other  parts  of  the  property. 
In  some  cases  where  this  has  been  the  case  similar  material 
has  not  been  found  or  only  by  going  great  distances. 

Most  states  now  have  a  department  of  geology  which  is 
pretty  thoroly  versed  in  the  formations  within  its  boundaries 
and,  as  such  information  is  for  the  public,  there  is  no  rea- 
son why  a  clayworker  or  prospective  clayworker  should  not 
benefit  by  it. 

WARE    TO    BE    MANUFACTURED 

It  is,  of  course,  primarily  important  that  a  company  should 
know  that  the  raw  material  on  the  property  being  consid- 
ered is  suited  to  the  ware  to  be  manufactured.  If  refrac- 
tories are  to  be  made,  it  is  necessary  to  know  that  there 
is  a  sufficient  quantity  of  clay  in  the  deposit  which  comes 
up  to  a  certain  standard  of  refractoriness.  If  face-brick  is 
the  object,  the  materials  must  develop  the  desired  colors. 
If  hollow  ware  or  pavers  are  required,  the  material  must  be 
suitable,  and  there  must  be  enough  of  it.  Even  experts 
cannot  determine  these  things  from  a  small  hand  sample 
or  a  barrel  of  clay  taken  from  the  surface  at  some  point  on 
the  property. 

MARKET 

In  selecting  a  property  the  item  of  location  in  regard  to 
market  must  be  kept  in  mind.  No  matter  how  good  the  raw 
material  may  be,  it  has  no  value  unless  it  can  be  delivered 
to  the  market  either  in  its  raw*  or  finished  state  at  a  profit. 
Many  plants  have  been  built  only  to  fail  because  this  could 
not  be  done.  The  vast  majority  of  factories  in  the  struc- 
tural products  end  of  the  business  must  have  a  local  market 
which  will  absorb  the  greater  percentage  of  their  product. 
In  only  isolated  cases  is  this  condition  reversed.  The  prox- 
imity of  a  market  is,  therefore,  an  important  consideration. 

In  a  few  localities,  especially  in  the  far  West,  the  plant  is 
located  at  the  market  and  the  raw  material  shipped  to  it. 
Such  a  condition  exists  because  the  freight  rates  are  lower 
on  raw  material  than  on  finished  products  and  because  all 


Testing  Clay  Properties  7 

of  the  plants  supplying  the  market  follow  the  same  method. 
SHIPPING  FACILITIES 

A  clay  products  plant  must  have  good  shipping  facilities, 
that  is,  it  must  have  good  railroad  service.  At  the  present 
date  this  is  not  a  difficulty  that  is  often  encountered.  Some- 
times a  plant  will  be  located  at  such  a  distance  from  a  rail- 
road that  a  large  expenditure  is  necessary  to  put  in  a  spur. 
Sometimes  from  ten  to  thirty  thousand  dollars  is  spent  in 
this  way,  the  interest  and  maintenance  necessarily  being 


Fig.   3.      Section    of    Hill    Showing    Overburden    or    Drift. 

charged  against  the  output.  In  such  cases  a  great  saving 
could  often  be  made  by  locating  the  plant  near  the  rail- 
road and  bringing  the  raw  material  to  it  on  an  industrial 
railroad  or  better  still,  locating  a  deposit  of  the  same  raw 
material,  nearer  the  railroad,  as  often  can  be  done  if  an  in- 
telligent search  is  made. 

Whenever  possible,  it  is  best  to  locate  within  reach  of  two 
competing  railroads  for  while  rates  are  generally  fixed,  the 
car  supply  will  always  be  much  better  and  the  troublesome 
matter  of  switching  charges  at  terminals  can  often  be 
avoided  thru  the  competitors  absorbing  them. 

WATER  SUPPLY 

Plants  do  not  often  have  to  worry  about  a  water  supply 
but  failure  to  look  into  this  matter  may  lead  to  much 
trouble,  especially  in  some  parts  of  the  country.  A  few 
years  ago  a  large  factory  was  erected  on  high  ground  and 


8         Clay  Plant  Construction  and  Operation 

about  ten  miles  from  the  nearest  stream.  Water  for  con- 
struction purposes  was  obtained  from  a  driven  well,  the 
water  from  which  was  salty.  No  thot  was  given  to  this 
water  until  operations  commenced,  when  it  was  found  to  be 
absolutely  unlit  for  either  boiler  or  tempering  purposes. 
Months  were  consumed  in  an  effort  to  locate  purer  water, 
but  to  no  avail:  There  remained  nothing  to  do  but  put  in 

STRATA      o^  ^MAUC 
CONTAINING     LiMt   o«    OTHER 
R.IOUA     IN4RC.OIK.NT3 


Fig.  4.     Section    of   Hill   Containing   Seams   of  Worthless   or 
Injurious    Material. 

expensive  condensers  or  pipe  to  the  stream  ten  miles  away. 
Trouble  arose  among  the  stockholders  over  this  location, 
with  the  result  that  the  plant  stood  idle  for  years  until 
finally  it  was  sold  for  about  twenty-five  per  cent,  of  its  cost. 
Having  taken  into  account  all  of  the  above  considerations, 
the  matter  of  testing  the  property  to  determine  the  amount 
and  value  of  the  material  to  be  used  must  be  tackled.  To 
dig  up  a  few  surface  samples  and  send  them  to  a  clay  ma- 
chinery company  or  testing  laboratory  is  utterly  useless. 
Surface  indications,  as  a  rule,  mean  nothing  so  far  as  shales 
and  clays  are  concerned. 

WHY  SYSTEMATIC   SAMPLING    IS   NECESSARY 

In  the  first  place  weathering  will  so  change  the  character- 
istics of  a  shale  or  clay  as  to  make  it  entirely  different  from 
the  unweathered  material  below.  Years  of  exposure  to  the 
elements  will  turn  a  hard,  rocky  shale  into  a  soft  plastic 
material  which  will  show  splendid  working  qualities,  where- 
as the  original  unweathered  material  will  resist  every  effort 


Testing  Clay  Properties  9 

to  turn  it  into  ware.  Also  a  buff  burning  clay  or  shale  may 
weather  into  a  red  burning  material,  sometimes  to  a  depth 
of  six  or  eight  feet.  Weathering  often  leaches  out  of  the 
surface  material  objectionable  constituents  whichj  would 
otherwise  prohibit  its  use.  On  the  whole  it  might  safely 
lie  said  that  the  testing  of  weathered  surface  samples  has 
caused  more  trouble  and  losses  than  any  other  item  con- 
nected with  the  selection  of  a  shale  or  clay  deposit. 

Land  slides  on  hill  sides  have  caused  much  trouble  where 
surface  samples  have  been  taken.  These  slides  sometimes 
extend  over  a  large  area  and  cover  the  material  under  them 
like  a  blanket.  In  some  cases  a  large  portion  of  a  hilltop 
will  have  broken  away  and  slid  to  the  bottom.  Beneath  it 
the  material  may  be  useless.  Under  such  conditions  sur- 
face testing  would  show  a  far  greater  quantity  of  material 
available  than  is  actually  the  case.  It  is  on  an  occasion  of 
this  kind  that  a  knowledge  of  the  geology  of  the  district 
becomes  valuable,  for  with  it,  it  would  be  readily  recognized 
that  something  was  cut  of  place. 

In  the  glacial  areas  surface  indications  count  for  little  or 
nothing.  Both  hills  and  valleys  are  more  often  than  not 
covered  with  a  worthless  drift.  Only  thoro  drilling  will 
disclose  the  material  beneath,  as  it  will  also  determine 
whether  the  overburden  is  too  heavy  to  make  the  locating 
of  a  plant  profitable. 

Glacial,  river  and  swamp  deposits  are  so  changeable  as  to 
make  it  absolutely  unsafe  to  accept  surface  indications.  The 


Fig  5.     River  Deposit  Showing  Varying  Thickness  of  Strata. 

very  nature  of  these  deposits  indicate  that  they  will  con- 
tain strata  or  pockets  of  sand  and  gravel  which  may  make 
the  entire  bed  worthless.  In  the  accompanying  sketches," 
Figs.  1  to  6,  some  of  the  above  described  conditions  are 
illustrated. 

To  properly  test  a  property  it  should  be  laid  out  in 
squares  similar  to  a  checker  board  (Fig.  7).  The  side 
of  each  square  should  be  100,  200  or  300  feet.  Each  in- 
tersection should  be  numbered  and  at  these  points  the  drill 


10       Clay  Plant  Construction  and  Operation 

holes  should  be  located.  It  is,  of  course,  only  necessary 
to  drill  test  holes  at  those  intersections  which  come  above 
the  grade  level  or,  if  the  bottom  of  the  bed  or  deposit  is 
known  to  come  some  distance  up  the  hill  sides,  above  that 
point.  When  the  pit  is  to  be  opened  below  grade  and 
the  property  is  flat,  a  drill  hole  should  be  located  at  each 
intersection. 

The  kind  of  drill  to  use  for  the  tests  depends  entirely 
upon  the  nature  of  the  deposit.  Soft  shales  or  clays  can  be 
drilled  with  a  hand  auger  drill,  but  where  gravel  seams  or 
strata  of  stone  occur  in  the  formation,  it  will  not  work.  A 
well  drill  will  go  thru  any  formation,  but  it  has  the  disad- 
vantage of  churning  up  the  material  in  the  hole  and  it  is, 
therefore,  not  altogether  a  safe  instrument  to  use  unless  an 
expert  is  on  the  job  to  watch  the  results.  The  diamond 
drill  is  the  best  instrument  for  this  kind  of  work  but  its 
use  usually  means  a  heavy  expense. 

HAND  AUGER   DRILL 

When  such  a  drill  can  be  used,  testing  becomes  a  simple 
operation.  The  equipment  costs  very  little.  It  merely 
consists  of  a  wood  auger  of  not  too  grea-t  a  pitch  about  a 
foot  long  and  \l/2  an.d  1^4  inches  in  diameter.  To  this  is 
welded  a  ^2-inch  steel  rod  about  five  feet  long,  the  upper 
end  of  which  is  threaded  with  a  pipe  thread.  A  handle  is 
provided  that  can  be  attached  to  this  rod  and  which  pro- 
vides a  good  leverage.  A  sufficient  number  of  sections  of 
half-inch  pipe  are  provided  to  lengthen  out  the  drill  as  it 
goes  down.  These  sections  should  be  about  four  feet  long. 
Each  time  the  drill  is  run  down  a  few  inches  it  is  pulled 
up  and  the  borings  which  come  with  it  are  examined  and 
preserved  for  further  tests.  If  the  holes  are  very  deep  it  is 
necessary  to  provide  some  means  of  pulling  out  the  long 
drill.  A  simple  three-leg  set-up  over  the  hole  with  a  block 
and  tackle  at  the  top  will  answer  this  purpose.  Two  men 
are  required  on  the  drill,  as  it  becomes  very  difficult  to 
turn  it  after  it  gets  down  a  few  feet. 

WELL  DRILL 

If  a  well  drill  is  used  it  is  customary  to  employ  some 
drilling  company  to  do  the  work.  In  ordinary  shales  and 
clays  such  a  drill  will  go  down  very  fast.  By  its  rate  of 
progress  the  hardness  of  the  various  starta  can  easily  be 
judged  by  an  engineer  but,  as  mentioned  above,  on  account 


Testing  Clay  Properties 


11 


of  the  condition  of  the  borings  as  they  are  lifted  out,  an 
inexperienced  man  could  .determine  very  little.  As  the 
borings  come  from  the  holes  in  a  soft  wet  condition  it  is 
necessary  to  dry  them  in  preparation  for  burning  and  dry- 
ing tests.  Of  all  the  methods  this  one  is  probably  the 
poorest,  altho  on  a  big  job  it  will  more  than  likely  prov< 
the  cheapest. 

DIAMOND   DRILL 

Diamond  drilling  is  very  expensive  but  the  results  ob- 
tained are  really  so  superior  to  all  other  methods  that  a 
cautious  company  cannot  afford  to  use  any  other.  By  this 
method  a  core  is  obtained  which  gives  a  complete  story 
of  the  formation  drilled  thru.  Strata  of  stone,  coal  and 
any  changes  in  the  clay  or  shale  are  shown  exactly  as 
they  occur.  The  cores  when  preserved  serve  to  show  the 
management  exactly  what  they  may  expect  to  encounter 


Fig.    6.     Section    of   Hill   Showing    Remainder   of   Lense   of   Flint 

Clay. 

and  allows  them  to  prepare  for  contingencies  long  before 
they  have  to  be  met. 

Diamond  drilling  is  done  by  companies  organized  for 
the  purpose  and  the  drills  are  in  the  hands  of  experts.  The 
work  is  usually  done  at  so  much  per  foot,  the  price  vary- 
ing according  to  the  material  to  be  drilled  thru. 


12       Clay  Plant  Construction  and  Operation 

From  two  to  five  thousand  dollars  spent  in  .diamond 
drilling  may  seem  like  a  large  sum  of  money,  but  it  is  a 
small  percentage  of  the  cost  of  a  modern  plant  whose  suc- 
cess depends  absolutely  upon  -the  raw  material.  Consid- 
ering the  number  of  companies  that  have  been  ruined  or 
have  in  the  end  paid  four  or  five  times  this  amount  in  or- 
der to  get  out  of  difficulties  caused  by  going  into  things 
blindly,  it  would  seem  to  be  the  better  part  of  wisdom  to 
spend  the  money  in  the  beginning,  even  tho  the  sum 
seems  large.  The  item  of  removing  overburden  alone  may 
amount  to  five  or  six  thousand  dollars  a  year  and  a  com- 
pany taxed  with  this  expense  would  have  probably  selected 
a  site  elsewhere  could  they  have  seen  beforehand  what 
they  were  going  up  against. 

Another  drill,  a  sort  of  little  brother  to  the  diamond 
drill  produces  the  same  results,  but  is  slower.  Instead  of 
using  diamonds  for  the  cutting  edge,  the  bit  is  of  tool 
steel  with  a  cutting  edge  like  a  saw.  This  drill  can  be 
operated  by  hand  or  a  gasoline  engine  and  can  be  pur- 
chased for  a  few  hundred  dollars.  The  cores  produced  are 
very  perfect  but  do  not  come  out  in  such  long  sections. 
This,  however,  is  not  detrimental. 

PRACTICAL  TESTS  NEXT  STEP  IN  PROCEDURE 

Having  drilled  the  property  thoroly,  it  is  then  necessary 
to  secure  sufficient  material  with  which  to  make  practical 
tests.  If  the  cores  or  material  from  the  drill  holes  show  the 
deposit  to  be  fairly  uniform  thruout,  this  is  a  simple  mat- 
ter. It  is  then  only  necessary  to  sink  a  pit  thru  the  weath- 
ered portion  on  the  surface  or  run  an  "open-cut"  into  the 
hillside  and  secure  a  sufficient  quantity  of  the  unweathered 
material  to  make  a  number  of  tests  on  the  kind  of  equip- 
ment it  is  proposed  to  use.  This  quantity  may  vary  from 
five  barrels  to  a  carload,  according  to  the  scope  of  the 
tests,  the  cautiousness  of  the  company  and  the  people 
making  the  tests.  It  is  utterly  useless  and  a  waste  of  time 
and  money  to  attempt  to  get  a  test  from  a  few  pounds  of 
material,  as  is  sometimes  done,  and  the  man  who  is  willing 
to  make  a  report  on  such  a  test  and  allow  money  to  be 
staked  upon  such  a  report  is  a  man  to  be  avoided. 

In  order  that  a  test  may  approach  as  near  actual  work- 
ing conditions  as  possible,  it  should  be  made  on  full  size 
equipment  and  on  the  types  of  ware  it  is  expected  to  man- 
ufacture. It  should  be  dried  as  nearly  as  possible  under 


Testing  Clay  Properties  13 

working  conditions.  The  burning  of  the  samples  can 
safely  be  done  in  a  test  kiln,  providing,  of  course,  the  tests 
are  in  the  hands  of  a  competent  man. 

CHECK  DRILLING  AGAINST  WORKING  SAMPLE 

The  material  from  -the  drill  holes  should  be  checked 
against  the  working  sample  in  order  to  be  certain  that  a 
variation  in  the  deposit  that  would  afreet  the  working  and 
other  qualities,  does  not  exist.  Such  check  tests  can  be 
made  in  several  ways.  Chemical  analysis  will  show  up  any 
decided  variation  and,  coupled  with  a  briquette  test,  in 
which  the  .drying,  shrinkage,  burning  and  color  qualities 
can  be  noted  and  compared,  will  provide  data  upon  which 
a  decision  can  be  made. 

When  a  formation  is  encountered  which  shows  varia- 
tions at  different  depths  it  is  absolutely  necessary  that  a 
test  be  made  on  each  of  the  different  materials.  To  neg- 
lect to  do  this  may  have  serious  consequences  for  it  has 
been  the  encountering  of  variations  in  the  bank  or  pit, 
after  a  company  has  started  operations,  that  has  caused  so 
much  trouble  in  the  past.  Along  the  Atlantic  coast  and 
in  the  mountainous  regions  of  the  West,  from  five  to  ten 
different  kinds  of  clay  may  be  encountered  in  a  depth  of 
forty  or  fifty  feet. 

Some  exceptions  can  be  made  in  the  case  of  refractory 
fireclay  .deposits.  These  clays  are  valuable  according  to 
the  degree  of  their  refractoriness.  Melting  tests  can  be 
made  from  the  cores  and,  there  is  hardly  any  necessity  for 
other  tests,  altho  they  may  be  made  as  a  precaution.  In 
dealing  with  these  clays,  the  drill  holes  should  be  placed 
very  close  together  as  a  deposit  may  vary  greatly  in  re- 
fractoriness, and  instead  of  being  continuous  over  a  large 
area  may  consist  of  a  number  of  small  deposits,  with 
barren  areas  between  them. 

COMPETENT     ENGINEER    SHOULD    SUPERVISE    TESTING 

It  is  a  safe  and  wise  plan  to  have  the  entire  work  of 
testing  the  property  and  material  done  under  the  super- 
vision of  a  competent  engineer.  It  is  a  job  for  an  expert 
and  no  one  else,  for  no  matter  how  thoroly  the  work  of 
testing  may  be  .done,  the  report  on  the  results  will  be  of 
no  value  unless  the  man  who  makes  it  knows  his  business. 

Testing  of  clays  or  shales  should  never  be  left  to  people 


14       Clay  Plant  Construction  and  Operation 


Testing  Clay  Properties  15 

who  are  interested  in  furnishing  the  plant  equipment.  No 
matter  how  conscientious  they  may  be,  in  the  nature  of 
the  case  it  is  absolutely  impossible  for  them  to  be  un- 
biased. More  often  than  not  they  are  not  to  blame  for 
misleading  reports,  as  they  often  have  no  means  of  know- 
ing the  history  of  the  samples  sent  them.  The  methods 
of  testing  used  are  also  open  to  criticism.  Material  which 
will  not  make  "nice  appearing"  ware  when  first  run  thru 
a  machine  is  run  over  and  over  again  until  the  desired  re- 
sults are  obtained.  This  is  not  a  practical  test,  for  even 
a  shale  or  clay  with  poor  working  qualities  can  be  made 
to  produce  good  ware,  if  it  is  worked  over  enough  times. 
A  little  more  thought  and  care  given  to  this  department 
of  the  industry  will  save  many  .dollars  to  investors,  and 
it  will  place  clayworking  in  a  much  better  light  with  those 
financial  interests  whose  assistance  is  becoming  more  nec- 
essary every  year  in  order  that  it  may  keep  pace  with  the 
other  great  industries  in  whose  ranks  it  properly  belongs. 


CHAPTER  II 
Hollow  Ware  Dies 


A  FEW  YEARS  AGO,  the  average  clayworker — or  brick- 
^*  maker — was  not  at  all  interested  in  the  subject  of  hol- 
low ware.  Its  manufacture  was  confined  to  comparatively 
few  companies  and  what  little  knowledge  on  the  subject  that 
a  few  men  possessed,  was  securely  locked  away  and  labeled 
''Trade  Secrets." 

As  has  often  proved  the  case  in  industries  other  than 
clay  working — and,  for  that  matter — in  clay  working  itself — 
these  "secrets"  contained  so  little  real  information  as  to 
be  worthless  to  the  industry  at  large;  and  so  today,  this 
important  and  rapidly  growing  line  of  clayworking  finds 
itself  attempting  to  progress  with  less  basic  knowledge, 
probably,  than  any  other  branch  of  the  industry.  For 
this  reason,  if  none  other,  the  matter  of  die  construc- 
tion and  die  adjustment  has  been  brought  into  the  lime- 
light and  an  insistent  demand  for  more  knowledge  is  ap- 
parent. 

The  hollow  ware  manufacturers  have  made  some  progress 
during  the  past  year  or  so,  in  fact,  so  much  progress  that 
literally  hundreds  of  brickmakers  have  been  tempted  to  "try 
their  hand  at  the  game."  It  is  these  brick  manufacturers,  who 
for  the  most  part,  have  taken  up  hollow  ware  as  a  side  line, 
who  are  suffering  most  thru  lack  of  knowledge  on  the  sub- 
ject of  dies,  or  rather  the.  lack  of  knowledge  on  the  entire 
subject  of  hollow  ware  manufacture. 

Naturally,  the  simple  thing  to  do  when  the  decision 
is  made  to  turn  out  a  small  tonnage  of  hollow  ware,  is 
to  convert  the  brick  machine  into  a  hollow  ware  ma- 
chine by  simply  buying  a  few  dies  constructed  so  as  to 
fit  the  front  of  the  machine.  Right  here  the  trouble  com- 
mences, for  a  brick  machine  and  a  hollow  ware  machine  are 
alike  in  appearances  only. 

16 


Hollow  Ware  Dies  17 

Brick  machines  are  built  with  taper  barrels  or  fronts. 
i...is  taper  is  designed  for  the  express  purpose  of  com- 
pressing the  clay  into  as  solid  a  mass  as  possible,  in  or- 
uer  that  a  dense  bar  may  emerge  from  the  die.  In  addi- 
tion to  tapering  the  barrel,  in  order  to  get  the  maximum 
bar  density,  the  pitch  of  the  auger  in  the  nozzle  is  only 
increased  enough  to  keep  the  area  constant.  This  in- 
crease in  the  density  of  the  clay  is  only  prevented  from 
doing  injury  to  the  barrel  front  or  die,  (or  else  reliev- 
ing itself  thru  the  hopper),  by  the  fact  that  a  brick  die  pre- 
sents a  fairly  large  opening — roughly  forty  square  inches. 

DIES    DEVELOPED    FROM    SEWER    PIPE    INDUSTRY 

111  reviewing  the  history  of  the  tile  industry  it  will 
be  found  that  for  years  all  hollow  ware  was  made  on 
sewer-pipe  presses.  As  is  well  known  these  presses  are 
straight  barrelled  affairs — they  have  no  taper  in  their 
entire  length.  This  fact,  and  also  the  fact  that  the  clay 
was  pushed  thru  the  die  by  a  plunger,  which  gave 
a  perfectly  equal  flow  over  the  entire  surface  of  the  die, 
made  them  absolutely  ideal  hollow  ware  machines  in  this 
respect.  Their  one  great  drawback  was  the  intermittent 
delivery. 

When  the  demand  came  for  increased  capacities,  the 
auger  machine  was  resorted  to.  Observation  soon  dis- 
closed the  fact  that  the  webs  of  tile  made  on  the  sewer-, 
pipe  press  were  of  sufficient  density  for  all  practical 
purposes  and  that  therefore  previous  compression  in  a  tap- 
ered machine  barrel  was  unnecessary.  In  addition  it  was 
soon  found  that  in  attempting  to  force  the  compressed  clay 
thru  the  limited  openings  of  a  tile  die,  the  dies  and  machines 
were  frequently  smashed,  an  excessive  amount  of  horse- 
power consumed,  and,  most  annoying  of  all,  the  clay  fre- 
quently insisted  on  backing  out  thru  the  hopper  in  preference 
to  going  thru  the  die. 

These  observations  led  to  the  development  of  the  mod- 
ern auger  hollow  ware  machine.  This  machine  has  a 
straight  barrel,  generally  a  continuous  screw  auger,  the 
pitch  of  which  is  constant  or  increases  toward  the  front, 
and  a  force  feed  attachment.  Sometimes  instead  of  the 
force  feed,  a  pug-mill  is  attached  which  serves  the  same 
purpose.  This  machine  does  not  compress  the  clay  in 
any  way  except  in  front  of  the  auger.  The  auger  merely 
solidifies  and  expresses  it  to  the  die  opening,  giving  at 


18       Clay  Plant  Construction  and  Operation 

the  same  time  the  greatest  speed  with  the  least  possible 
consumption  of  power. 

The  differences  between  the  brick  machine  and  the  tile 
machine,  altho  seemingly  slight,  are  really  great,  in  fact, 
great  enough  in  many  cases  to  make  the  difference  be- 
tween success  and  failure. 

Of  course,  considerable  hollow  ware  is  made  on  or- 
dinary brick  machines,  but  when  they  are  used,  the  many 
troubles  which  are  encountered  when  even  the  most 
perfect  equipment  is  used,  are  magnified  a  hundred-fold, 
and  what  is  more  important,  the  user  is  losing  the  bene- 
fit of  all  the  work  and  investigation  that  is  at  present 
going  on  in  the  effort  to  eliminate  the  troubles  of  this 
branch  of  the  industry:  For  it  is  obviously  impossible 
to  get  investigators  to  spend  time  experimenting  with 
machines  which  they  know  to  be  unfit  for  the  work  re- 
quired. 

DIE   TROUBLES    MAY   ORIGINATE    ELSEWHERE 

That  successful  die  construction  and  adjustment  is 
not  confined  to  work  on  the  dies  alone,  the  author  will 
attempt  to  point  out  in  the  following.  The  fact  is,  so 
many  other  items  enter  into  the  consideration,  that  the 
die  might  almost  be  considered  as  of  secondary  im- 
portance. Many  clayworkers  have  spent  months  and 
even  years  and  wasted  thousand  of  dollars  in  experi- 
menting with  dies,  only  to  find  that  all  of  their  trouble  came 
from  other  sources,  which  were  overlooked  because  they 
were  not  understood. 

On  the  other  hand,  adjusting  a  die  so  that  it  runs  out 
ware  that  dries  and  burns  safely  is  not  enough.  "Ton- 
nage" is  the  cry  in  the  tile  industry,  and  "tonnage"  musi 
be  gotten.  It  is  therefore  necessary  to  so  build  and  ad- 
just the  dies  that  the  greatest  possible  column  speed 
may  be  reached.  Many  dies  are  built  which  will  "run" 
successfully  at  a  low  speed,  but  when  an  attempt  is  made 
to  get  any  respectable  tonnage  out  of  them,  they  are 
absolutely  useless. 

When  a  clayworker  orders  a  hollow  ware  machine  there 
is  one  item  which  should  receive  his  most  careful  at- 
tention ;  that  is,  to  see  that  the  auger  or  main  shaft  is  abso- 
lutely central  in  the  barrel.  It  will  even  pay  to  make  the 
trip  to  the  factory  before  the  machine  is  shipped  in  order 
to  satisfy  himself. 


Hollow  Ware  Dies  19 

No  one  can  estimate  the  amount  of  die  trouble  that 
has  been  caused,  and  the  money  lost,  thru  time  con- 
sumed in  taking  off  and  putting  on  dies,  and  thru  cracked 
ware,  simply  because  this  shaft  was  not  properly  located. 

It  is  naturally  expected  that  machines  come  from  the 
factory  in  perfect  condition,  but  in  the  past  this  has  not 
always  been  the  case.  The  experienced  tile  makers  look 
for  such  defects,  but  the  man  who  is  just  getting  into 
the  game  is  not  very  likely  to  look  for  trouble  in  the  machine 
as  soon  as  it  arrives. 

Very  often  the  auger  shaft  on  a  used  machine  will  be 
slightly  sprung,  and  this  is  even  worse  than  having  it  out 
of  center.  It  is  practically  impossible  to  successfully  make 
ware  on  a  machine  in  this  condition,  as  the  auger  changes 
the  lines  of  pressure  on  each  revolution..  In  the  case  of  the 
shaft  which  is  not  central,  the  pressure  is  always  released 
at  the  point  where  the  circumference  of  the  auger  is  farth- 
est from  the  sides  of  the  barrel. 

SPEED  OF  MACHINE— EFFECT  ON  DIES 

The  speed  of  the  machine  is  a  very  important  factor.  A 
die  may  be  built  which  will  run  out  ware  at  a  slow  speed — 
say  ten  feet  per  minute — which  will  pass  thru  the  dryer  in 
perfect  conditon.  But  if  an  attempt  be  made  to  speed  up 
the  machine  so  as  to  make  fifteen  feet  per  minute,  the  re- 
sulting ware  is  a  dead  loss. 

Some  clayworkers  upon  finding  this  to  be  the  case,  have 
provided  for  the  machine  a  drive  from  a  separate  engine,  or 
better  still,  from  a  variable  speed  motor.  To  resort  to  these 
methods  in  most  cases,  however,  is  foolish,  to  say  the  least. 
The  clayworker  who  "goes  after"  such  a  die  and  so  adjusts 
it  that  he  gets  from  twenty  to  thirty  feet  per  minute  is  more 
than  repaid  for  the  trouble  taken. 

When  a  machine  is  being  driven  too  fast  for  a  die,  the  lat- 
ter invariably  develops  fast  and  slow  areas.  Sections  of  the 
die  which  give  the  least  resistance  to  the  clay  flow,  either 
thru  webs  or  walls  or  the  location  of  bridges,  will  be 
fast  in  proportion  to  other  sections.  In  cases  which  are  not 
bad,  the  ware  may  appear  good  enough  to  go  into  the  drier, 
but  will  come  out  cracked.  In  extreme  cases  the  column 
will  tear  up  as  it  leaves  the  die.  The  remedy  for  this 
trouble  will  be  taken  up  later  in  this  chapter. 

In  determining  the  speed  at  which  a  machine  should  be 
driven,  the  raw  material  enters  very  little  into  the  considera- 


20       Clay  Plant  Construction  and,  Operation 

tion.  Of  course,  clays  and  shales  vary  enough  to  make  some 
difference,  but  they  are  not  the  determining  factor.  When  a 
machine  is  to  be  driven  at  constant  speed,  the  most  important 
point  to  be  considered  is  the  relation  between  the  size  of 
the  largest  die — or  rather  the  largest  tile — which  will  be 
made,  and  the  capacity  of  the  barrel  of  the  machine. 

When  the  auger  is  driven  at  too  great  a  speed  on  a  large 
tile,  there  is  not  sufficient  compression  in  front  of  it  to  give 
equal  pressure  over  the  whole  die.  This  is  due  to  the  large 
amount  of  openings  in  the  die,  the  clay  getting  away  com- 
paratively too  fast.  There  is  practically  nothing  that  can  be 
done  to  a  die  to  eliminate  this  trouble.  With  a  lower  speed, 
the  clay  gets  a  chance  to  gather  between  the  auger  and  the 
die,  the  space  forming  a  sort  of  reservoir,  and  it  is  then  com- 
pressed and  flows  out  evenly  thru  the  die  openings. 

When  a  machine  which  can  only  be  run  at  one  speed  is 
used  to  make  a  variety  of  sizes  it  is  necessary  to  determine 
the  speed  acording  to  the  size  of  the  large  tile.  Many  mod- 
ern hollow  ware  plants  have  separate  units  for  the  large  and 
small  sizes,  thus  getting  away  from  the  difficulty.  This,  how- 
ever, is  not  a  general  rule. 

While  it  is  obviously  impossible  to  give  the  best  auger  speed 
on  account  of  the  great  variety  of  raw  materials,  the  speeds 
most  widely  used  range  from  20  to  25  R.  P.  M.  In  a  few 
cases  the  auger  is  run  up  as  high  as  50  R.  P.  M.,  but  such 
practice  is  condemned  by  hollow  ware  manufacturers  gener- 
ally. The  machine  or  auger  speed  is  another  troublesome 
item  in  connection  with  the  converted  brick  machine.  Brick 
machines  are  always  run  at  higher  speeds  than  tile  ma- 
chines, or  at  least  should  be,  and  unless  the  machine  speed 
is  lowered  for  hollow  ware,  trouble  is  almost  certain  to 
ensue. 

TYPES   OF    DIES 

For  all  practical  purposes  hollow  ware  dies  may  be  con- 
sidered as  being  of  two  types,  viz.:  flat  and  tapered  (see  Fig. 
8).  Flat  dies  are  always  dry,  but  the  tapered  type  may  be 
either  dry  or  lubricated.  There  is  practically  no  difference 
in  the  methods  of  adjusting  the  two  types  when  run  dry,  but 
difficulty  is  often  experienced  with  lubricated  dies,  due  to  their 
complicated  construction.  True,  they  are  less  likely  to  give 
trouble  when  first  started,  but  like  all  tile  dies  their  "middle 
name  is  'Trouble' ".  It  may  be  well  to  note  in  this  connection 
that  the  large  manufacturers  use  dry  dies,  and  this  fact 


Hollow  Ware  Dies 


21 


should  be  enough  to  convince  beginners  that  this  kind  of  die 
is  the  best,  not  only  to  begin  with,  but  to  stick  to. 

In  the  flat  type  the  openings  are  almost  always  straight, 
i.  e.,  the  sides  of  the  die  plate  and  the  sides  of  the  cores  are 
parallel  thru  the  entire  thickness  of  the  die.  In  the  tapered 
type  the  die  tapers  on  all  sides  down  to  the  face  plate,  thru 
the  thickness  of  which  only  are  the  sides  of  the  die  parallel 
with  the  sides  of  the  cores. 

POINTS   ON    TAPER    OF    DIE 

The  taper  or  angle  of  the  openings  of  a  die  present  one 
of  the  most  interesting  problems  in  die  construction  and  ad- 
justment, in  fact  the  speed  of  the  column  issuing  from  any 
die  is  regulated  by  this  taper  or  angle. 


Fig.   8.     The   Two   Types   of    Hollow   Ware    Dies. 

When  the  tapered  die  was  first  introduced,  the  idea  of  the 
taper  was  to  give  a  slight  compression  to  the  clay  before  it 
issued  from  the  die  plate.  Each  die  manufacturer  had  his 
own  ideas  as  to  the  amount  of  taper  a  die  should  have,  de- 
pending somewhat  upon  the  clay  or  shale  that  was  to  be 
worked. 

A  few  of  the  more  progressive  hollow  ware  manufacturers 
have  found  that  the  amount  of  taper  given  a  die  is  of  the 
utmost  importance.  No  rules  or  laws  which  might  govern 
this  can  be  laid  down,  for  each  individual  clay  or  shale  re- 
quires a  separate  treatment;  that  is — each  clay  or  shale  or 
mixture  will  develop  its  greatest  column  speed  when  run 
thru  a  die  with  a  certain  taper. 


22       Clay  Plant  Construction  and  Operation 

In  some  cases  this  taper  is  so  slight  as  to  be  almost 
negligible,  in  others,  it  is  considerable.  In  order  to  find  the 
proper  taper  for  any  material,  it  is  necessary  to  make  a  die 
of  some  soft  material— preferably  wood.  It  should  be  made 
with  perfectly  straight  openings  and  the  cores  should  be  of 
the  same  material.  When  put  on  the  machine  the  column 
speed  should  be  noted  constantly.  As  the  clay  wears  away 
the  material  of  which  the  die  is  made,  the  bar  will  speed 
up  until  a  certain  point  is  reached— the  peak—aiter  which  the 
speed  will  drop  constantly. 

As  soon  as  the  column  reaches  the  greatest  speed,  the  angle 
of  wear  should  be  noted.  Two  or  three  trials  may  be  neces- 
sary to  determine  this  point,  but  when  it  is  once  obtained 
it  may  be  worth  thousands  of  dollars  a  year  to  a  manufac- 
turer. One  of  the  important  points  to  note  is  that  as  the 


Fig.  9.    Showing  Maximum  Speed  Taper  for  a  Theoretical  Clay. 

taper   is   increased   beyond  a  certain  point  the  column  gets 
constantly  slower  (see  Fig.  9). 

This  is  exceedingly  important  to  the  manufacturer  who  is 
buying  "stock"  or  ready-made  dies.  How  does  he  know  but 
that  the  dies  he  is  buying  have  a  taper  far  greater  than  his  raw 
material  will  stand?  Probably  a  die  with  more  or  less  taper 
would  increase  his  tonnage  from  twenty-five  to  a  hundred  per 
cent,  especially  on  certain  kinds  of  slow  running  tile.  One 
thing  should  be  borne  in  mind  in  this  connection — no  taper 
at  all  is  far  better  than  too  much.  The  increase  in  column 
speed  from  the  no  taper  point  to  the  maximum  speed  taper 
is  often  little  or  nothing,  but  beyond  the  maximum  speed 
taper  the  column  invariably  slows  down. 

In  order  to  take  care  of  the  wear  on  the  dies,  some  manu- 
facturers build  them  with  less  taper  than  is  required  to  pro- 
duce the  maximum  speed,  and  allow  the  die  to  wear  to  the 
proper  angle — passing  which  it  is  rebuilt  or  relined. 
AVOID    LONG   MOUTH    DIES 

To  make  a  die  exactly  right  originally  would  mean  that 


Hollow  Ware  Dies 


practically  from  the  moment  it  was  put  on  the  machine  it 
would  get  slower.  The  slowing  down  of  the  column  is 
caused  by  the  wedging  effect  which  the  day  gets  in  passing 
thru  an  opening  which  is  wider  at  the  point  of  entrance  than 
at  the  point  of  exit.  The  mixture  of  clay  grains  and  water 
can  be  compressed  up  to  a  certain  point,  but  beyond  that 
point  no  more  compression  is  possible  and  the  clay  wedges 
as  it  attempts  to  pass  thru. 

A  difficulty  often  experienced  in  the  taper  type  die,  and 
this  is  especially  true  of  dies  with  considerable  taper,  is 
the  springing  of  the  cores  out  of  positon.  The  great  length 
of  the  cores  and  posts  and  the  excessive  compression  within 
the  die  itself  combine  to  make  this  a  common  trouble.  Some- 
times "spreaders" — small  screws  or  pins  (Fig.  10) — are  used 
to  overcome  this  difficulty,  but  care  must  be  taken  that  these 
are  not  placed  too  close  to  the  front  of  the  die,  as  they  will 
develop  cracks  in  the  ware. 
When  cores  are  forced  even  a 
sixteenth  of  an  inch  out  of 
place,  the  loss  of  ware  in  the 
dryer  is  Hkely  to  be  great. 

A  long  mouth  die,  or  in 
other  words,  a  long  die,  should 
be  avoided  whenever  possible. 
A  short  die  is  much  less  likely 
to  cause  trouble,  is  lighter  to 
handle,  and  consumes  far  less 
power.  Clay  workers  often 
contend  that  only  one  type  of 
die  will  work  on  their  particu- 
lar material,  when  the  fact  is 
that  they  have  never  tried  any 
other,  nor  tried  to  improve  on 
the  ones  they  use.  It  is  sim- 
ply a  case  of  their  having 

started  with  one  type  and  continued  to  use  it,  altho  it  is 
quite  possible  that  it  may  be  the  most  troublesome  type  they 
could  possibly  use.  Lack  of  initiative  in  this  direction,  .as  in 
many  others  in  this  industry,  is  responsible  for  much  of  the 
tile  makers'  trouble. 

AFFECT  OF  RAW  MATERIALS  ON  DIE 

Raw  materials,  that  is,  the  clay  or  shale  which  is  used — 
naturally  have  a  very  considerable  bearing  on  the  type  of  die 


Fig.  10.  Showing  Spread- 
ers for  Keeping  Cores  from 
Shifting. 


24       Clay  Plant  Construction  and  Operation 

as  well  as  on  its  construction  and  methods  of  adjustment. 
Some  materials  slip  thru  a  die  like  so  much  grease,  while 
others  offer  a  very  strong  resistance.  Furthermore,  some 
materials  can  be  run  thru  a  die  in  a  very  soft  condition, 
while  others  have  to  be  very  stiff.  It  is  apparent  that  under 
these  conditions,  a  wide  variation  in  die  construction  is  pos- 
sible. 

Where  an  easy  running  machine  is  used,  the  dies  can  be 
built  very  light,  the  bridge  and  posts  being  reduced  to  a  mini- 
mum. On  the  other  hand,  where  a  hard  running  clay  is  used, 
or  where  it  is  necessary  to  run  it  very  stiff,  the  bridges  must 
be  heavy  and  strong.  Light  die  construction  usually  produces 
fast  dies,  while  heavy  construction  tends  to  produce  slow 
ones.  As  a  general  rule,  it  may  be  said  that  a  die  with  con- 
siderable metal  behind  it  will  require  more  adjusting  than 
one  with  less. 

Every  ounce  of  metal  added  to  the  back  of  a  die  offers  re- 
sistance to  the  clay  flow — in  other  words,  acts  as  a  baffle. 
It  therefore  pays  well  to  closely  study  the  raw  materials  avail- 
able, in  order  to  so  handle  them  that  the  lightest  possible 
construction  may  be  used  in  the  die  and  behind  it. 

It  is  a  noticeable  fact  that  weathered  materials  slip  thru 
a  die  easier  than  unweathered  materials.  Most  clay  and 
shale  banks  have  a  covering  of  weathered  material.  When 
care  is  taken  to  get  the  maximum  percentage  of  this 
weathered  material  mixed  with  every  load  that  goes  to  the 
pans,  the  best  results  are  generally  obtained.  When  enough 
of  this  material  is  not  available  to  get  the  best  results,  un- 
weathered material  should  be  weathered  whenever  possible. 

Many  clayworkers  would  be  surprised  at  the  results,  in 
the  way  of  increased  column  speed,  the  lowering  of  power 
consumption  and  the  reduction  of  die  wear  that  follow  the 
use  of  material  that  has  been  given  even  a  slight  weathering, 
as  compared  with  the  results  obtained  with  unweathered  ma- 
terial. 

A  slight  weathering  may  be  given  by  shooting  ahead  at  the 
bank  with,  of  course,  due  precaution  for  the  mixing  of  this 
material  with  that  which  is  newer.  Very  often  the  addition 
of  the  small  percentage  of  surface  clay  (when  this  is  avail- 
able) will  have  a  beneficial  effect  upon  column  speed,  power 
consumption  and  die  wear. 

Fineness  of  grain  (or  fine  grinding)  has  a  far  greater  effect 
.on  tile  dies  than  most  clayworkers  realize.  Coarse  materials 
will  invariably  slow-up  a  die  and,  in  most  instances,  make 


Hollow  Ware  Dies  25 

the  column  "drag"  at  the  corners.  The  author  has  observed 
cases  where  new  screen-plates  in  the  pans,  and  new  screens 
ahead  of  the  pug-mill  have  "speeded-up"  a  whole  set  of 
dies  from  eight  to'  ten  feet  per  minute,  and  at  the  same  time, 
eliminated  the  "dragged"  corners.  Whenever  a  die  slows 
down  for  no  apparent  reason,  look  at  the  plates  in  the  pans 
and  see  if  the  screen-boy  is  attending  to  his  business. 

It  must  be  remembered,  too,  that  the  drying  qualities  of 
the  raw  material  have  a  very  considerable  bearing  upon  the 
die  and  upon  its  proper  adjustment.  Some  clays  will  go 
thru  a  dryer  without  loss,  even  when  run  on  a  die  that  is 
decidedly  unbalanced.  Others  require  dies  that  are  in  the 
most  perfect  adjustment.  Gases  are  known  where  it  seemed 
practically  impossible  to  run  ware  on  certain  dies  without 
excessive — it  may  be  said  prohibitive — dryer  loss,  and  where 
it  was  found  that  various  substances  could  be  added  to  the 
clay  that  would  make  it  work  with  these  same  dies,  and 
without  a  marked  dryer  loss. 

The  most  common  of  these  materials  is  "grog" — ground- 
up  burnt  ware.  This  is  ground  in  the  pans  with  the  clay  or 
shale.  Other  substances  very  successfully  used  are  tannic 
acid  in  crystalline  form,  common  salt,  raw  limestone  and 
slacked  lime.  Sometimes  less  than  one  per  cent  of  these  sub- 
stances will  overcome  very  bad  cases.  The  raw  limestone 
and  salt  have  especially  proved  successful. 

Even  with  clays  which  dry  easily  and  with  dies  that  are  per- 
fectly balanced,  heavy  losses  will  occur  if  ware  is  "rushed" 
thru  the  dryers.  While  there  are  materials  which  will  not 
stand  a  progressive  tunnel-dryer  treatment,  there  are,  fortu- 
nately, many  that  do  not  require  the  slower  hot-floor  or  open- 
room  treatment.  Experiment,  patience,  and  a  great  fund 
of  common  sense  are  important  requisites — in  fact,  the  onlv 
guides. 

ONE   VERY   IMPORTANT   POINT 

Brickmakers  and  other  clayworkers  have,  in  many  in- 
stances, unsuccessfully  attempted  to  make  hollow  ware. 
After  a  comparatively  short  trial  they  have  given  it  up,  with 
the  impression  that  the  available  raw  materials  were  not 
suitable.  In  the  writer's  opinion,  the  clay  was  blamed  for 
the  fault  in  the  men,  who  did  not  have  the  "stick-to-it"  qual- 
ity that  is  necessary  to  success. 

The  author  believes  it  perfectly  safe  to  say  that  any  ma- 
terial from  which  other  structural  products  are  made  can  be 


2$       Clay  Plant  Construction  and  Operation 

successfully  used  in  the  manufacture  of  hollowware.  Plants 
have  been  known  to  work  for  two  years  or  more  before 
successfully  solving  their  problems,  during  all  of  that  time 
meeting  with  a  loss  of  from  one-quarter  to  three-quarters 
of  all  of  the  ware  that  was  made.  But  in  the  end,  they 
were  able  to  successfully  work  the  available  raw  material 
and  with  losses  that  were  very  inconsiderable. 

The  surface  clays  of  eastern  Canada  are  unquestionably 
the  most  difficult  to  handle  on  this  continent,  no  matter  whst 
products  are  made  from  them.  In  spite  of  this,  four  large 
plants  are  manufacturing  fire-proofing  from  them,  and  are 
turning  out  a  product  that  will  compare  favorably  with  any- 
thing in  this  line  made  at  any  other  point  in  America,  and 
with  less  loss  than  the  average  American  plant. 

These  results  were  not  accomplished  without  years  of  ex- 
perimenting and  a  large  money  outlay,  but  they  stand  as  a 
lasting  record  of  what  can  be  done  with  "impossible"  ma- 
terials, if  the  nerve  and  determination  is  there  to  make  those 
materials  "possible." 

The  "never-say-die"  rule  should  be  adopted  by  every  clay- 
worker  who  goes  into  the  hollowware  game.  Before  start- 
ing, however,  he  should  get  all  of  the  information  that  it  is 
possible  for  him  to  obtain,  regarding  his  material.  Then 
he  should  go  after  information  relative  to  dies  and  machines 
When  he  comes  to  the  point  where  he  must  select  one  type 
of  die,  he  should  work  with  that  type  until  he  becomes  ac- 
quainted with  his  own  peculiar  and  particular  requirements, 
and  then,  with  the  original  die  as  a  starting  point,  evolve 
a  die  that  is  suitable  for  his  materials.  Radical  changes 
almost  always  mean  starting  all  over  again.  It  pays  to  go 
slow. 


CHAPTER  III 


Factors  Important  to  Dies 


pROBABLY  LESS  IS  KNOWN  about  scientific  auger 
•*•  construction  than  about  any  other  subject  connected 
with  the  hollowware  or  brick  industry.  Practically  all  of  the 
progress  that  has  been  made  has  been  thru  the  efforts  of  the 
men  who  make  clayworking  machinery  in  their  attempts  to 
provide  augers  to  suit  the  various  materials  that  have  been 
met  with.  No  data  is  available  and  only  a  few  general  rules 
are  adhered  to.  One  thing,  however,  is  known;  that  is,  that 
the  design  of  an  auger  for  hollowware  should  be  different 
from  that  of  an  auger  that  is  used  in  the  manufacture  of 
brick.  In  the  former,  the  diameter  remains  constant,  with  the 
pitch  sometimes  constant,  but  generally  increasing;  in  the 
latter,  the  diameter  decreases  with  the  pitch  constant,  or  in- 
creases only  enough  to  maintain  the  area  between  the  flights 
constant. 

All  three  types  of  augers,  single,  double  and  triple  wing 
are  used.  The  single  wing  is  the  fastest,  without  question, 
bu;  as  a  rule  the  die  must  be  placed  so  far  from  the  auger 
(in  order  to  overcome  the  unequal  flow  and  the  lamination) 
that  this  advantage  is  lost.  The  single  wing  auger  also  has 
a  great  tendency  to  make  dies  flow  fast  in  the  center  and 
to  cause  lamination.  This  often  necessitates  heavy  baffling 
at  that  point,  which  reacts  against  speed. 

As  a  general  rule  the  single  wing  auger  is  to  be  avoided, 
especially  by  the  man  who  is  inexperienced.  Equal  pressure 
over  the  face  of  the  die  is  hardest  to  get  with  this  type, 
and  warped  ware — especially  with  thin  shapes — often  results 
from  its  use. 

The  double  wing  auger  is  most  generally  used  and  gives 
good  results,  altho  there  are  cases  where  the  triple  wing 
has  made  a  marked  improvement  over  it.  Theoretically 
the  triple  wing  should  be  best  and  give  the  least  amount  of 

27 


28       Clay  Plant  Construction  and  Operation 

die  trouble,  on  account  of  the  even  pressure  given  the  column. 
Three  wings,  however,  displace  considerable  clay  in  the  ma- 
chine barrel,  which  may  be  a  serious  matter  where  large 
tile  are  to  be  made.  Also  more  friction  i?  set  up  in  the 
barrel  and  more  power  consumed,  and  where  hard  running 
clays  are  encountered  this  may  seriously  interfere  with 
column  speed. 

In  some  cases,  the  auger  is  run  thru  the  barrel  as  a 
continuous  screw.  This  may  be  single  part  of  the  way  and 
double  the  balance,  or  double  all  the  way;  in  the  case  of  a 
triple  wing  it  may  begin  as  a  single  under  the  hopper,  then 
change  to  double  and  finally  change  to  triple  at  the  tip. 

In  other  cases  the  screw  is  broken  in  the  sections  back 
of  the  tip  or  ordinary  knives  are  used,  as  in  a  brick  machine. 
Materials  vary  so  much  that  only  by  experimenting  in  each 
case  can  the  best  type  be  determined.  It  will  pay  handsome- 
ly, however,  to  spend  a  little  money  in  this  direction,  as 
results  vary  greatly  in  every  case. 

One  of  the  most  annoying  troubles  encountered  in  tile 
manufacture  is  due  to  auger  wear.  A  die  may  be  made  to 
run  perfectly  and  at  a  satisfactory  speed  with  a  new  auger 
which  has  been  run  just  long  enough  to  get  a  polish,  but 
this  same  die  will  begin  to  be  troublesome  as  soon  as  the 
auger  begins  to  wear  at  the  circumference  and  a  space  is 
opened  up  between  it  and  the  barrel.  This  space  around 
the  auger  offers  a  point  of  release  for  the  clay  and  allows 
it  to  slip  back,  in  other  words,  it  allows  the  pressure  to  be 
released  at  the  outside  corners  and  walls  of  the  die,  while 
the  center  keeps  up  its  speed. 

The  result  is  an  unbalanced  die  and  the  necessity  for 
baffles  in  the  center.  Just  as  soon,  however,  as  a  new  auger 
is  put  on,  the  center  is  slow  and  these  baffles  must  be  re- 
moved or  smaller  ones  substituted.  Taking  care  of  this 
auger  wear  is  a  serious  problem  and  one  that  is  met  in  prac- 
tically no  other  branch  of  the  industry. 

ALLOY  STEEL  AUGERS. 

In  the  author's  opinion,  hollowware  manufacturers — espe- 
cially the  larger  ones — who  have  made  no  move  in  this  direc- 
tion would  do  well  to  abandon  the  ordinary  chilled  semi- 
steel  auger  which  loses  its  "skin"  in  a  short  time,  and  ex- 
periment with  augers  of  alloy-steels  such  as  manganese, 
chrome,  nickel  or  vanadium. 

Some  have  done  this  and  given  it  up  as  a  bad  job  simply 


Factors  Important  to  Dies  29 

because  it  took  too  long  to  give  them  a  polish.  The  mat- 
ter of  polishing'an  auger  is  another  annoying  problem  to  the 
tilemaker,  and  one  that  can  be  eliminated  to  a  great  extent 
if  he  will  tackle  it  in  the  right  way. 

Taking  a  certain  die  for  example,  which  under  good  con- 
ditions will  run  12,000  ft.  per  day;  when  a  new  auger  is  put 
on,  this  same  die  will  run  5,000  ft. — probably  the  second 
day  it  will  run  7,000  ft,  the  third  day  10,000  ft.  and  on  the 
fourth  day,  will  be  up  to  capacity. 

The  total  loss  of  10,000  ft.  of  ware  or  practically  a  day's 


Fia.   11. — Section   of  Auger   Flight 
With    and   Without   Ltp. 


run  with  a  value  of,  say,  $250  is  chargeable  to  "polishing 
the  auger,"  and  this  may  happen  every  twenty  to  fifty  days, 
according  to  the  raw  material. 

Now  is  such  a  loss  necessary?  Some  tilemakers  have 
come  to  the  conclusion  that  it  is.  How  many  of  the  augers 
used  come  from  the  manufacturers  with  just  the  rough 
spots  knocked  off  the  casting  with  a  grinding  wheel?  Prob- 
ably 98  per  cent.  And  where  is  the  real  polishing  done?  In 
the  machine,  and  at  a  cost  of  from  $200  to  $500 ;  for  besides 
the  actual  loss  in  ware,  the  overhead  expenses  must  be  added 
and  the  increased  power  consumption  of  the  machine. 

Cutting  down  the  expense  is  really  a  rather  simple  matter; 
if  the  auger  had  been  polished  before  it  went  into  the  ma- 
chine the  trouble  would  be  practically  eliminated,  for,  as 
one  of  the  clay  machinery  companies  recently  remarked  in 
an  advertisement:  "The  machine  is  not  the  place  to  polish 
the  auger." 

If  the  clayworker  would  insist  on  it  and  pay  for  it,  un- 
doubtedly the  machinery  people  would  polish  the  augers  to 
a  glasslike  smoothness.  If  they  will  not  or  cannot,  the  clay- 
worker  can  himself  install  a  portable  grinding  and  buffing 
wheel  with  a  flexible  shaft,  at  less  than  half  the  cost  of 
polishing  one  auger  in  the  machine,  and  with  a  labor  cost 
of  $5  or  less,  grind  and  buff  every  auger  until  it  shines 
like  a  mirror.  Of  course,  even  with  this  done  the  auger 
will  not  get  up  to  speed  for  a  few  hours  or  a  day,  but  so 


30       Clay  Plant  Construction  and  Operation 

little  difference   would  be-  noted   that  the  terrors  of  a  new 
auger  would  be  no  more. 

Tilemakers  who  are  using  an  auger  without  a  lip  (Fig.  11), 
would  do  well  to  have  one  put  on  their  pattern.  Such  a  lip 
adds  considerable  life  to  the  auger  by  keeping  the  edge  from 
so  rapidly  wearing  away. 

When  the  barrel  liners  of  a  machine  have  worn  to  such 
an  extent  that  considerable  space  is  left  around  a  new  auger, 
it  is  time  to  consider  a  new  set  of  liners.  Worn  liners  have 
the  same  effect  on  a  die  as  a  worn  auger,  and  tend  to  seri- 
ously decrease  the  life  of  an  auger  by  allowing  the  clay  to 
slip  back  around  it.  One-half  inch  is  considered  the  maxi- 
mum space  that  should  be  allowed  around  an  auger  and 
this  is  often  too  much. 

DISTANCE  OF  AUGER  FROM   DIE 

Hollowware  machines  are  supplied  with  extension  rings 
so  that  a  die  may  be  placed  at  its  proper  working  distance 
from  the  auger.  This  distance  is  exceedingly  important  in 
die  adjustment  and  much  trouble  comes  from  the  fact  that 
many  clayworkers  give  the  matter  no  consideration.  Tile 
of  no  great  variation  in  size  can  generally  be  run  at  the 
same  distance,  once  the  proper  distance  is  determined.  But 
when  there  is  a  great  difference  in  size  the  distance  mil 
change  with  the  majority  of  raw  materials.  The  proper  dis- 
tances cannot  be  specified  under  any  circumstances,  as  it  is 
absolutely  a  matter  of  experiment.  The  type  of  machine, 
speed  of  machine,  raw  material  and  dies  are  all  determining 
factors. 

The  increase  or  decrease  in  this  distance  will  often  cor- 
rect die  trouble  without  anything  further  being  done.  A 
die  which  will  not  make  a  single  good^tile  when  placed  five 
inches  from  the  auger  tip  may  run  splendidly  at  ten  inches. 

It  should  be  borne  in  mind,  however,  that  with  each  frac- 
tional increase  in  the  distance  of  the  auger  from  the  die,  the 
power  consumption  of  the  machine  is  greatly  increased.  It 
is  therefore  necessary  to  place  the  die  as  close  as  possible 
and  still  get  good  results. 

Warping  and  cracking  is  often  caused  by  having  the  die 
too  close  to  the  auger.  This  is  due  to  the  weave  given  the 
column  by  the  auger.  When  the  die  is  very  close,  this  weave 
is  noticeable  as  the  column  runs  out;  but  at  other  times  it 
does  not  show  up  until  the  ware  is  dry. 

It  is  always  well,  therefore,  when  attempting  to  adjust  a 


Factors  Important  to  Dies  31 

die  to  be  sure  the  distance  is  correct,  for  in  many  cases  noth- 
ing can  be  accomplished  unless  that  is  first  made  right. 

Another  matter  connected  with  this  distance  (and  very  im- 
portant in  some  cases  where  large  tile  are  made)  is  that  the 
space  between  the  die  and  auger  acts  as  a  reservoir  from 
which  the  clay  is  evenly  forced  thru  the  die  by  the  "push"  of 
the  auger  behind  it.  Unless  this  reservoir  is  large  enough,  or, 
in  other  words,  the  bulk  of  the  clay  between  die  .and  auger 
is  great  enough,  the  auger  action  or  pressure  is  likely  to  be 
localized,  the  tendency  being  towards  fast  flow  in  the  center 
and  slower  flow  at  the  outside.  This  trouble  is  usually  over- 
come by  baffling  the  center  of  the  die,  which  will  neces- 
sarily slow  the  column  and  cut  capacity.  A  correction  can 
often  be  made  by  increasing  the  distance  of  die  from  auger 
without  a  reduction  of  speed. 

It  has  become  an  accepted  fact  that  in  order  to  secure 
the  best  results,  the  barrel  of  the  machine  must  be  pro- 
portionate to  the  size  of  ware  made  with  it.  This  means  that 
a  well  designed  hollow-ware  plant  will  have  at  least  two  ma- 
chines— one  for  the  smaller  tile  and  one  for  the  larger. 

Competent  authorities  seem  to  agree  that  for  such  tile  as 
4-in.  by  12-in.,  3-in.  by  12-in.  and  5-in.  by  8-in.  column  cov- 
ering, Denison  tile,  etc.,  the  barrel  should  be  16-in.  to  17-in. 
in  diameter,  while  for  the  larger  tile,  the  barrel  should  be 
only  slightly  larger  than  is  required  for  the  largest  size. 

The  difficulty  which  arises  when  a  large  barreled  machine 
is  used  for  small  tile  is  that  the  clay  itself  forms  a 
tapering  nozzle  between  auger  and  die,  thereby  creating  the 
same  conditions  as  are  encountered  in  the  use  of  a  tapered 
nozzle  machine.  This  causes  excessive  compression  of  the 
clay,  and  a  reduction  of  the  possible  column  speed. 

FORCE   FEED 

The  tile  manufacturer  has  gradually  come  to  the  realiza- 
tion that  a  force  feed  apparatus  of  some  sort  is  an  absolute 
necessity.  There  are  a  number  of  these  on  the  market  and 
most  of  them  have  nrerit.  Of  course,  where  a  pug-mill  is 
combined  with  the  machine  it  acts  as  a  force  feed  apparatus. 

Some  raw  materials  absolutely  require  a  mechanical  force 
feed  to  assist  the  auger  to.  keep  up  the  necessary  pressure 
behind  the  die.  In  these  cases  even  constant  hand  punching 
at  the  hopper  will  not  prevent  the  uneven  pressure  from 
causing  much  loss  at  the  dryer. 


32       Clay  Plant  Construction  and  Operation 

There  can  be  little  question  that  in  many  cases  where  a 
man  is  kept  constantly  punching  at  the  hopper  in  lieu  of  a 
mechanical  feed,  more  or  less  mysterious  die  trouble  occurs, 
due  to  constantly  changing  die  pressure  and  flow.  The  cause 
may  not  be  traced  to  this  source,  but  it  is  reasonable  to  sup- 
pose that  no  matter  how  conscientious  the  "human  force  feed" 
may  be  (and  it  is  often  a  boy  who  doesn't  know  what  "con- 
scientious" means)  he  will  let  up  on  his  work  at  times.  A 
car  of  ware  comes  thru  the  dryer  in  pretty  bad  shape  in  the 
midst  of  others  in  perfect  shape.  There  is  much  theorizing 
as  to  the  cause  and  very  often  everything  is  blamed  but  the 
right  thing — the  "human  force  feed." 

Even  where  a  mechanical  feed  is  used,  care  must  be  taken 


Fig.    12.      Showing    Method    of   Correcting    Fast    Flow    in 
Center   by   Use   of  Steel    Plates   or  Shims   on    Cores. 

to   make   the   pug-mill   keep   the   hopper    full   or   the   same 
mysterious  dryer  losses  will  occur. 

DISTRIBUTION    OF    METAL    ON    BACK    OF    DIES 

In  the  foregoing  the  writer  has  attempted  to  treat  in  de- 


Factors  Important  to  Dies  33 

tail  those  factors  outside  of  the  dies  which  have  an  effect 
on  die  construction  and  adjustment.  It  will  be  readily  seen 
that  it  is  almost  a  hopeless  proposition  to  successfully  tackle 
the  dies  themselves  unless  some  knowledge  is  possessed  of 
the  factors  mentioned.  And  while  a  few  clayworkers  are  so 


Off  .Cg«sj 


Fig.   13. 


Showing    Method   of   Balancing    Die   by   Opening   Up 
Slow   Walls  or  Webs. 


fortunate  as  to  have  raw  materials  which  can  be  literally 
"murdered"  and  which  make  the  tile  business  seem  like 
child's  play,  it  is  not  so  with  the  vast  majority.  The 
great  trouble  with  the  tile  business  is  that  a  clayworker  starts 
out  with  one  die,  generally  a  simple  one,  which  may  give 
little  trouble,  but  inside  of  a  year  or  two  he  finds  himself 
with  anywhere  from  ten  to  fifty  dies,  and  in  the  meantime 
he  has  found  his  difficulties  increasing  and  his  lack  of 
knowledge  of  the  "fine  points"  very  disconcerting. 

Coming  to  the  dies  themselves,  it  is  found  that  the  distribu- 
tion of  the  metal  at  the  back,  in  the  shape  of  bridges,  cores, 
bridge-posts,  nuts,  studs,  etc.,  has  an  important  bearing  on 
the  working  of  them.  It  will  be  readily  understood  that  any- 
thing placed  back  of  the  die  opening,  if  only  a  single  thin 
bridge,  will  interfere  with  the  equal  flow  of  the  clay  thru 
the  die  opening  and  also  the  speed  of  that  flow. 

It  should  therefore  be  the  object  of  the  die  builder  to  re- 
duce this  interference  to  a  minimum  by  making  the  bridges, 
posts,  cores,  etc.,  as  light  as  the  service  required  of  them 
will  stand.  It  is  also  important  that  these  metal  parts  be 
distributed  over  the  back  of  the  die  as  evenly  as  possible. 


#4       Clay  Plant  Construction  and  Operation 

This  will  balance  the  "interference"  and  cause  the  clay  t<? 
flow  evenly.  If  this  is  not  done  and  the  bridges  (for  in- 
stance) are  concentrated  over  any  particular  part  of  the  die, 
the  resulting  interference  with  clay  flow  at  that  point  will 
produce  a  slow  area.  This  will  probably  have  to  be  counter- 
balanced by  baffles  over  the  fast  areas,  the  result  being  that 
the  column  speed  will  be  considerably  reduced. 

A  close  study  of  his  dies  in  action,  together  with  a  little 
experimenting,  will  soon  teach  a  clayworker  to  easily  over- 
come many  die  troubles  by  a  slight  shifting  of  the  bridges 
and  posts. 

Two  instances  that  have  come  to  the  author's  attention  are 


Fig.  14.  On  Left,  Original  Shape  of  Jamb  Tile  Die  Decidedly 
Unbalanced.  On  Right,  New  Shape  of  Jamb  Tile  Die  Perfectly 
Balanced. 

cited;  a  partition-die  allowed  a  fast  flow  in  the  center  and 
was  baffled  at  the  point  in  order  to  balance  it.  The  two  out- 
side bridges  (it  was  a  three  core  die)  were  moved  ^-in. 
closer  to  the  center.  The  cores  were  reset  so  that  all  webs  and 
walls  remained  exactly  as  before.  The  result  was  a  perfectly 
balanced  die  without  the  use  of  baffles,  and  which  pro- 
duced over  1,000  feet  more  ware  per  day. 

In  the  other  case  the  ^-in.  nuts  which  held  the  bridges  down 
on  the  bridge-posts  were  removed,  and  the  bridges  pinned  to 
the  posts  instead.  The  removal  of  even  this  slight  amount 
of  metal,  (about  one  pound)  increased  the  die  speed  almost 
ten  per  cent. 

It  will  invariably  be  found  best  to  avoid  baffling  a  die  with 
metal  plates  if  such  a  thing  be  possible.  Sometimes  it  is 
not  possible  and  then  they  must  be  resorted  to.  Generally 
it  entails  more  work  to  get  a  balanced  die  by  other  methods, 
but  it  always  pays  if  tonnage  and  power  consumption  count 
for  anything. 

When  a  new  die  is  put  on  the  machine  it  must  get  a  certain 
amount  of  wear  before  it  gets  "set."  The  bridges,  cores  and 
other  parts,  must  get  a  polish  before  anything  definite  can  be 
told  as  to  the  final  results  it  will  give.  In  such  cases  it  is 


Factors  Important  to  Dies  35 

wise  to  use  baffles  where  necessary.  It  may  be  found  that 
after  a  short  time  it  will  run  well  enough  without  the 
baffles,  but  if  it  does  not,  a  move  should  be  made  to  correct 
its  faults. 

If,  for  instance,  the  middle  cross- webs  or  web  is  very 
much  faster  than  the  balance  of  the  die,  a  shim  consisting 
of  a  thin  piece  of  steel  can  be  fastened  to  the  cores,  thus 
making  the  fast  webs  slightly  thinner.  Sometimes  1/32-in. 
will  be  enough  (Figures  12  and  16).  It  is  seldom  that  even 
J-6-in.  in  web  thickness  will  effect  the  sale  or  safety  of  a 
tile,  so  that  this  ordinarily  cannot  be  an  objection. 

If,  however,  the  webs  cannot  be  made  thinner  (on  account 
of  reducing  the  safety  factor)  a  thin  cut  on  the  sides  of  the 
cores  next  to  the  slow  walls  or  webs,  thus  slightly  increasing 
the  thickness  of  these  walls  or  webs,  will  have  the  same  effect 
by  speeding  up  the  slow  portions  of  the  die,  as  is  shown  in 
Figure  13.  When  it  is  only  a  single  wall  or  web  that  is  slow, 
it  is  very  easy  and  effective  to  open  up  the  die  at  this  point 
This  is  very  much  better  practice  than  baffling  the  entire  die 
down  to  the  speed  of  this  slow  portion. 

Occasionally,  a  tile  is  of  such  a  shape  that  one  or  more  of 
its  webs  are  very  much  thicker  than  all  the  others.  Naturally 
such  a  die  is  very  difficult  to  handle.  A  die  of  this  type  and 
a  method  of  balancing  it  is  shown  in  Figure  14.  In  the  original, 
the  wide  wall  was  so  much  faster  than  the  balance  of  the  die 
thai  very  large  baffles  were  necessary.  The  resistance  to  the 
clay  flow  was  so  great  that  finally  the  die  was  broken.  The 
second  die  works  periectly  without  the  use  of  the  baffles  and 
is  aDout  five  feet  faster  per  minute. 

SCORtRS    AND    SCRATCHERS 

The  type  of  scorer  or  scratcher  used  has  a  very  consider- 
able effect  on  the  die.  Some  form  of 
dovetail  grooving  is  used  on  almost  all 
modern  plants,  but  the  methods  of  pro- 
ducing it  differ.  Whatever  the  design 
of  the  scorers,  their  shape  has  a  ten- 
dency to  drag  at  the  walls  of  the  tile, 
invariably  slowing  them. 

As  the  grooving  is  absolutely  neces- 
sary, the  speed  of  the  whole  die  must  F|      1g     Too| 
be    made    to    conform    to    the    grooved          steel     Scorer, 
walls.  However,  the  number  of  grooves          Adjustable, 
make    a    very    considerable    difference 
and    this    may    often    be    taken    advantage    of    in    adjusting 


#6       Clay  Plant  Construction  and,  Operation 


a  die.  If  a  die  has  a  slow  wall  on  which  are  six  grooves, 
a  reduction  to  five  or  four  may  be  all  that  is  necessary  to 
correct  the  trouble.  Similarly  a  fast  wall  may  be  slowed 
down  by  the  addition  of  one  or  more  grooves  or  by  the  widen- 
ing of  them.  When  flat  steel  scorers  are  fastened  on  the 
outside  of  the  die  they  can  be  moved  in  or  out  to  make  more 
or  less  resistance.  (See  Figure  15.)  These  are  simple  ex- 
pedients and  should  be  taken  advantage  of  at  every  oppor- 
tunity. 

METAL   BAFFLES 

When  it  is  impossible  to  take  advantage  of  any  other 
method,  the  metal  plate  must  be  resorted  to  to  prevent  local 
fast  areas  in  a  die.  The  plate  is  fastened  to  the  die  plate  or 
bridge,  according  to  the  location  of  the  trouble.  This  method 
of  adjustment  is  very  simple,  but  its  use  leads  to  increased 
power  consumption,  often  a  slow  running  columns,  smashed 
bridges  and  sometimes  smashed  dies. 

There  are  times  when  a  me^al  baffle  is  absolutely  neces- 
sary. A  die  may  be  so  constructed  that  a  thin  core  will  be 
so  exposed  to  the  clay  pressure  that  it  shifts,  thereby  unbal- 
ancing the  die.  In  such  cases  a  small  baffle  is  placed  on  top 

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Fig.  16.  On  Left,  Original  Tile;  in  Center,  First  Attempt  at 
Balancing;  at  Right,  Second  Attempt  at  Balancing,  with  Die 
Perfectly  Balanced. 

of  the  bridge  in  such  a  position  that  some  of  the  pressure 
is  taken  off  the  exposed  side  of  the  core,  allowing  it  to  re- 
tain its  normal  position.  Care  should  be  taken  to  make  a 
baffle  as  small  as  possible  and  still  get  desired  results,  and 


Factors  Important  to  Dies 


37 


never  to  use  a  baffle  until  every  other  means  has  been  ex- 
hausted. 

BRIDGE   CRACKS 

Bridge  cracks  are  the  hollow-ware  maker's  bugbear.  There 
is  unquestionably  more  trouble  from  this  source  than  any 
other,  yet  (strange  as  the  statement  may  seem)  it  is  often 
the  easiest  to  overcome. 

When  the  clay  is  parted  by  the  bridge  it  must  be  given  a 
certain  distance  and  a  certain  amount  of  pressure  in  which 
to  "weld"  again.  Some  materials  are  of  such  a  physical 
nature  that  they  will 
do  this  in  one  inch  of 
travel,  while  others 
require  from  three  to 
six  inches.  In  pre- 
venting bridge  cracks 
the  tapered  die  is 
supposed  to  have  a 
decided  advantage 
over  the  flat  die,  in 
that  the  clay  is  given 
a  slight  compression 


oH 


Fig.    17.      Serrated    Bridge   to    Pre- 
vent Bridge  Cracks, 
after     passing     the 

bridge.     However,  close  observation  of  the  two  have  failed 
to  give  either  an  advantage  in  this  respect. 

When  a  bridge  crack  occurs,  one  thing  is  shown  plainly  and 
that  is  that  the  clay  had  not  sufficient  opportunity  to  knit 
from  the :  time  it  passed  the  bridge  until  it  issued  from  the 
die,  or  putting  it  another  way — the  bridge  was  too  close  to 
the  point  of  issue.  Probably  setting  the  bridge  back  a  Y2  In. 
would  overcome  the  difficulty  entirely  or  it  might  be  neces- 
sary to  move  it  three  or  four  inches. 

Materials  vary  so  much  in  their  knitting  or  "welding" 
qualities  that  only  by  experiment  can  the  proper  distance  be 
determined.  If  a  die  turns  out  bridge  cracked  ware  the 
bridges  should  be  moved  back  a  little  at  a  time,  until  the 
trouble  ceases,  and  cease  it  surely  will  when  the  proper  dis- 
tance is  found.  As  a  general  rule,  when  once  the  proper 
distance  is  determined,  all  bridges  can  safely  be  placed  at 
that  distance,  but  occasionally  some  one  die  will  require  a 
separate  treatment. 

Various  means  are  used  to  assist  the  clay  in  knitting.  One 
of  these  is  to  serrate  or  "saw-tooth"  the  bottom  of  the 


38       Clay  Plant  Construction  and  Operation 

bridges.  (See  Figure  17.)  Another  is  to  wrap  a  chain  around 
the  troublesome  bridge.  However,  where  it  is  necessary  to 
resort  to  the  latter  device  it  is  best  to  move  the  bridge  back 
slightly,  as  the  chain  has  to  be  constantly  replaced.  The 
temper  of  the  clay  may  have  a  bearing  on  bridge  cracking. 
Some  material  will  knit  readily  when  given  a  certain  temper 
and  refuse  to  knit  when  the  clay  is  not  so  treated. 

DIE   WEAR 

The  openings  in  a  die  are  subject  to  the  constant  abrasive 
action  of  the  material  forced  thru  them.  Some  materials 
being  more  gritty  than  others  wear  dies  faster,  but  all  dies 
wear  out  sooner  or  later.  Just  when  a  die  is  worn  out  and 
ready  for  the  scrap-heap  or  the  machine  shop  is  a  matter  that 
is  difficult  to  decide.  Dies  of  the  ordinary  cast-iron  variety, 
when  built  for  speed,  begin  to  slow  up  and  act  badly  very 
quickly.  With  progressive  manufacturers  this  "slowing  up" 
means  that  the  die  is  ready  for  the  discard.  Other  manu- 
facturers continue  to  use  a  die  until  it  almost  refuses  to  run 
a  column.  It  will  readily  be  seen  that  this  is  a  short  sighted 
policy,  for  not  only  does  the  loss  of  from  two  to  ten  (or 
more)  feet  per  minute  amount  to  a  considerable  tonnage  in 
even  a  day's  run,  but  the  increased  thickness  of  the  walls 
and  webs  adds  considerably  to  the  cost  of  manufacture  and 
to  the  freight  when  the  ware  is  shipped. 

As  has  been  previously  mentioned,  when  the  angle  of  the 
die  opening  passes  a  certain  point,  the  column  begins  to 
slow  down,  and  it  becomes  increasingly  slower  as  the  angle 
becomes  greater.  Furthermore,  the  wear  on  the  die  plate  and 
the  cores  so  affects  the  flow  that  it  becomes  increasingly 
difficult  to  keep  the  die  balanced. 

As  a  well  built  die  costs  from  $25  to  $50  a  tile  maker  has 
only  to  sit  down  and  figure  an  equal  loss  in  tonnage  and  cost 
to  find  out  when  his  dies  are  worn  out,  no  matter  what  the 
appearances  may  be. 

Brickyard  scrap  piles  are  often  fearful  and  wonderful 
sights,  but  most  fearful  and  wonderful  of  all  are  the  scrap 
heaps  of  some  hollow-ware  plants,  especially  some  of  the 
larger  ones.  It  is  undoubtedly  good  practice  to  withdraw 
from  use  a  worn  die,  and  it  is  unquestionably  bad  practice 
to  use  a  die  which  has  to  be  thrown  away. 

Quite  a  number  of  manufacturers  have  developed  dies 
which,  with  minor  repairs,  practically  last  forever.  In  such 
dies  the  cores  are  lined  with  replacable  tempered  tool-steel 


Factors  Important  to  Dies  39 

plates.  All  wearing  surfaces  except  the  bridges  are  lined 
with  the  same  material.  Others  line  the  dies  and  cores  in 
the  same  way  with  mild  steel  or  cast-iron.  The  author  has 
never  seen  a  type  of  dry  die  which  could  not  be  lined  and 
relined  in  this  way,  altho  the  original  relining  might  be  diffi- 
cult in  some  cases.  However,  if  it  is  too  difficult  a  proposi- 
tion there  can  be  no  reason  why  the  type  should  not  be  so 
modified  as  to  permit  of  its  being  done  and  thus  cut  out 
a  source  of  loss.  At  any  rate,  there  can  be  no  reason  why 
ordinary  cast-iron  should  be  used  at  all.  Far  better  wearing 
materials,  which  can  be  as  easily  machined,  are  available 
at  up-to-date  foundries,  and  case-hardening  of  most  of  the 
wearing  parts  is  not  a  difficult  matter.  Unfortunately,  to 
follow  such  suggestions  increases  the  first  cost  of  a  die 
(possibly  one-third)  and  this  is  almost  always  an  objection 
to  the  clayworker,  even  tho  such  expenditures  pay  dividends 
in  the  long  run. 

TOOL  STEEL  DOES  NOT  SLOW  UP  DIE 

Objection  is  heard  in  some  quarters  to  the  use  of  certain 
materials  in  die  construction,  for  instance,  tool-steel,  it  being 
often  claimed  that  this  material  slows  a  die.  After  numer- 
ous experiments,  the  author  cannot  believe  that  this  objection 
is  valid,  no  matter  what  the  qualities  of  the  raw  material 
may  be.  Such  claims  are  generally  based  on  theories  or 
experiments  which  have  never  been  followed  thru,  or  are 
advanced  by  men  who  are  afraid  to  step  off  the  beaten  paths 
they  have  trodden  all  fcheir  lives. 


CHAPTER  VI 


Dryer  Details 


T  T  IS  NOT  THE  INTENTION  of  the  author  to  go  into 
A  a  lot  of  theoretical  calculations  pertaining  to  the  evapo- 
ration of  moisture,  size  of  flues,  vents  and  stacks,  because 
such  calculations  are  absolutely  useless  to  the  average  clay- 
worker.  It  is  rather  the  intention  to  stick  almost  entirely 
to  constructional  details  and  suggestions,  and  especially  to 
those  which  are  so  often  overlooked  and  which  lead  to  those 
annoyances  to  which  so  many  dryers  are  heir. 

In  the  first  place,  dryer  troubles  would  be  far  less  fre- 
quent if,  before  constructing  one,  clay  plant  owners  would 
Consult  with  experts  in  this  particular  line.  This  does  not 
mean  consulting  a  man  who  has  one  particular  type  of  dryer 
to  build  or  sell,  but  rather  consulting  several  of  them  and 
also  obtaining  the  advice  of  an  expert  who  has  nothing  to 
sell  at  all. 

DRYERS  REQUIRE  MUCH  CARE  AND  THOUGHT 

There  is  no  other  part  of  a  clay  plant  that  requires  so  much 
care  and  thought  in  its  design  and  construction  as  does  the 
dryer.  Any  one  of  a  dozen  different  makes  of  machines  will 
grind  the  raw  material  or  form  the  ware,  and  any  one  of 
a  dozen  kinds  of  kilns  will  burn  it,  but  it  is  almost  impos- 
sible to  pick  out,  promiscuously,  one  of  the  many  kinds  of 
dryers  available  and  not  run  against  losses  which  at  times 
are  appalling. 

A  certain  type  of  dryer  may  do  splendid  work  on  stiff-mud 
brick  made  of  an  easy  drying  clay,  but  will  not  work  at 
all  on  those  made  of  a  tender  clay.  Again,  one  dryer  will  do 
excellent  work  on  a  stiff-mud  brick,  but  will  not  dry  success- 
fully, soft-mud  brick  of  the  same  material.  One  dryer  of 
the  tunnel  type  will  handle  successfully,  hollow-ware  on  the 
continuous  principle,  while  another  tunnel  dryer  would  have 
to  be  operated  on  the  intermittent  principle,  in  order  to  safely 
dry  the  same  ware  from  the  same  clay. 

40 


Dryer  Details  41 

Many  clayworkers  who  have  been  long  in  the  business  are 
coming  or  have  come  to  the  realization  that  there,  is  a  great 
deal  more  to  the  drying  end  of  the  business  than  they  had 
supposed.  Some  of  them  who  have  duplicated  time  and 
again,  drying  units  which  appeared  to  them  to  be  best  adapted 
to  their  particular  case,  have  found  that  for  years  past  it 
would  have  been  possible  to  have  installed  systems  which 
would  have  saved  large  amounts  of  money  thru  greater  speed 
with  smaller  losses. 

Putting  aside  the  consideration  of  open-air  dryers,  the 
primary  object  of  all  artificial  dryers  is  to  get  rid  of  the 
moisture  in  the  ware  with  the  greatest  speed  at  the  lowest 
cost,  at  the  same  time  having  due  consideration  for  the  safety 
of  the  ware.  To  obtain  these  results  certain  well-known 
principles  or  laws  must  be  observed.  Among  the  most  im- 
portant of  these  is  the  one  requiring  that  all  dryers  must  be 
so  designed  that  the  first  stage  of  the,  drying  be  carried  on 
at  very  moderate  temperatures  and  with  only  a  slight  move- 
ment of  the  surrounding  atmosphere  or  else  in  a  very  moist 
atmosphere  at  higher  temperatures  and  with  a  decided  move- 
ment of  the  surrounding  atmosphere.  Dryers  designed  to 
produce  the  latter  conditions  are,  as  a  general  rule,  the  most 
efficient  in  every  respect.  Those  designed  to  produce  the 
first  mentioned  conditions  reproduce  in  reality,  the  conditions 
found  in  an  open  air  dryer,  their  only  advantage  being  a 
heating  apparatus  which  makes  them  independent  of  weather 
conditions. 

OPEN    AIR    DRYERS 

In  spite  of  the  advances  made  by  the  industry  in  late  years, 
more  open-air  dryers  are  in  use  than  is  generally  supposed. 
Most  01  tnese,  naturally,  are  to  be  found  on  plants  using  the 
soft-mud  process  which  are  operated  only  during  the  sum- 
mer months.  The  drying  is  generally  done  in  racks,  the 
pallets  being  wheeled  out  on  trucks  and  later  again  moved 
by  trucks  from  the  racks  to  the  kilns. 

The  cost  of  drying  under  these  conditions  is  quite  high, 
in  fact  higher  than  in  most  artificial  dryers.  There  are  sev- 
eral reasons  for  this,  the  principal  one  being  the  several 
handlings  necessary  between  the  machine  and  kilns.  On 
large  plants,  too,  the  drying  racks  cover  a  large  area  and 
the  distances  covered  by  the  truckers  is  considerable.  On 
many  plants  the  investment  in  racks  amounts  to  a  large  sum 
and  the  exposure  to  the  elements  causes  excessive  deprecia- 
tion. 


42       Clay  Plant  Construction  and  Operation 

Many  clayworkers  using  this  method  of  drying  have  sought 
for  a  means  of  eliminating  some  of  these  bad  features  with- 
out going  to  the  expense  of  erecting  dryer  buildings. 


Fia-    18-     Dryer    Car    with    Weather    Protector. 


The  following  method  is  suggested  as  a  method  of  over- 
coming the  difficulties  encountered  with  the  racks.  Any 
number  of  tracks  of  a  length  convenient  to  the  layout  of  the 
plant  are  laid  down  in  the  open.  Regular  soft-mud  rack  cars, 
stiff-mud  or  hollow-ware  cars  are  provided  of  exactly  the 
same  type  and  gauge  as  used  in  artificial  dryers.  Each  car 
is  provided  with  a  removable  sheet  metal  "roof"  which  can 


Dryer  Details  4B 

be  tilted  so  as  to  protect  the  ware  from  rain  and  sun.     The 
idea   is   shown  in  Fig.  18. 

The  greatest  advantage  of  this  system  is  that  the  ware  is 
placed  on  the  cars  at  the  machine  and  not  handled  again  un- 
til it  is  run  into  the  kiln.  There  is  also  the  great  ad- 
vantage of  having  both  cars  and  rails  ready  for  immediate 
uce  should  it  be  decided  to  erect  an  artificial  dryer  at  any 
future  time.  Other  advantages  are  the  decidedly  lower  up- 
keep on  cars  over  wooden  racks  and  the  elimination  of  a  very 
bad  fire  risk  which,  in  most  cases,  is  non-insurable. 

INITIAL    COST    LITTLE    GREATER    THAN    FOR    RACKS 

The  difference  in  first  cost  is  slightly  in  favor  of  the  racks, 
but  with  the  ever-increasing  cost  of  lumber,  this  is  not  as 
much  as  would  be  supposed.  Then,  too,  in  case  an  artificial 
dryer  is  ever  built,  the  investment  in  racks  is  a  total  loss 
whereas  there  is  practically  no  loss  in  connection  with  the 
cars  and  tracks. 

Very  often  a  company  starts  out  with  insufficient  capital 
to  erect  dryer  buildings  and  permanent  kilns  and  uses  the 
open  air  method  until  able  to  afford  better  equipment.  In 
such  cases  this  method  of  drying  is  ideal,  as  there  is  no 
waste  of  capital  involved. 

The  method  is  also  useful  on  hollow-ware  plants  making 
large  shapes  which  are  difficult  to  dry  safely  in  an  artificial 
dryer.  Such  an  open  air  system  can  be  used  during  the  sum- 
mer months  when  a  stock  of  the  troublesome  shapes  can 
be  laid  in  to  carry  over  the  winter  months. 

If  necessary,  a  low  wooden  framework  can  be  built  on  tha 
outside  of  the  two  outer  tracks,  from  the  top  of  which  rolls 
of  canvas  can  be  dropped  to  protect  the  outside  cars  from 
driving  rains.  The  cars  on  the  inside  tracks  are  so  close 
together  that  there  is  no  danger  to  the  ware  from  this  source. 

DRYER    BUILDINGS 

Whatever  the  type  of  artificial  dryer  built  it  must  have 
walls  and  a  roof.  In  many  cases  it  has  apparently  been  con- 
sidered unnecessary  to  give  a  thought  to  the  materials  which 
have  been  used  in  the  construction  of  the  building.  Lumber 
has  been  very  popular,  especially  on  the  smaller  plants.  Brick 
has  naturally  been  used  most,  while  concrete,  especially  in 
roof  construction,  has  had  its  share  of  users.  Strange  to 
lay,  hollow-tile  has  found  favor  with  very  few  constructors. 

Primarily,  of  course,  the  shell  of  the  building  is  there  for 


44       Clay  Plant  Construction  and  Operation 

the  purpose  of  preventing  the  escape  of  the  heat  to  the  at- 
mosphere until  it  has  done  its  work.  It  is  not  the  idea  of 
the  clay  worker  that  only  part  of  the  heat  which 'he  puts  mto 
the  building  shall  do  work;  on  the  contrary,  it  is  his  earnest 
desire  that  all  of  it  shall  be  utilized.  Yet,  in  spite  of  this 
fact,  how  much  effort  is  made  to  prevent  radiation,  to  say 
nothing  of  more  direct  losses  of  heat?  In  not  more,  than 
one  dryer  in  one  hundred  has  there  been  the  slightest  effort 


Fig.    19.     Showing    Outer    W&II    of    Dryer   with    Air    Space    and 
Plaster. 

made  to  prevent  radiation  losses,  and  this  in  spite  of  the  fact 
that  on  the  other  ninety-nine  plants  the  great  cry  is  for  more 
heat  for  drying  purposes.  At  ordinary  drying  temperatures 
insulation  of  walls  and  roof  is  an  extremely  simple  matter; 
one  in  fact,  that  does  not  even  involve  extra  cost. 

The  use  of  lumber  cannot  be  too  strongly  condemned  for 
many  reasons.  In  the  first  place,  lumber  anywhere  about  a 
clay  plant  increases  the  fire  risk.  When  used  in  a  dryer  it  is 


Dryer  Details  45 

especially  dangerous,  for  parts  of  the  building  are  always 
as  dry  as  tinder,  and  no  matter  what  the  method  of  heating 
may  be,  there  is  always  a  danger  of  a  fire  being  started  with- 
in the  building  itself.  Frame  buildings  of  this  type  are 
nearly  always  "thrown  together"  with  the  consequence  that 
in  a  short  time  they  become  as  open  as  a  sieve.  Even  when 
care  is  taken  to  insulate  the  walls,  the  effort  nearly  always 
fails,  due  to  green  lumber  and  the  temperature  maintained 
within. 

Even  the  lumber  men,  who  formerly  built  all  of  their  dry- 
ers of  wood,  are  rapidly  abandoning  this  type  of  construction. 
One  lumber  company  recently  made  the  statement  that  their 
new  dryer,  which  was  built  of  hollow-tile  and  had  replaced 
an  especially  well-built  frame  dryer,  was  showing  a  saving 
of  twenty-five  per  cent,  in  fuel  and  drying  the  lumber  in 
twenty-five  per  cent,  less  time. 

Of  all  the  materials  available,  lumber  is  the.  least  suited 
to  the  purposes  of  dryer  construction. 

BRICK  WITH  AIR  SPACE  FORMS  GOOD  DRYER  WALL 

Brick  is  an  excellent  material  for  wall  construction,  pro- 
viding the  walls  are  built  with  an  air  space.  In  a  dryer  Luild- 
ing  (while  it  is  not  necessary  in  order  to  carry  the  roof  load 
unless  the  second  floor  is  used)  it  is  best  to  build  the  walls 
one  and  a  half  brick  thick  as  shown  in  Fig.  19.  It  will  be 
noted  that  the  air  space  is  broken  by  header  courses.  This  is 
done  to  break  up  air  currents  which  otherwise  would  be  set 
up  in  the  air  space  and  which  would  have  free  flow  from 
bottom  to  top  of  walls.  It  may  seem  strange  to  specify  a 
coat  of  plaster  on  the  inside  of  the  outside  walls,  but  this 
has  been  found  to  give  such  excellent  results  that  sooner  or 
later  it  is  bound  to  come  into  general  use.  On  test,  the  dif- 
ference between  the  radiation  thru  a  plastered  and  unplast- 
ered  wall  is  really  remarkable.  A  wall  plastered  on  both 
sides  will  radiate  twenty  per  cent  less  heat,  and  a  wall 
plastered  on  one  side  approximately  ten  per  cent,  less  than 
an  unplastered  wall.  Clayworkers  who  are  now  troubled 
with  cold  outside  tunnels  would  do  well  to  note  this. 

The  plaster  will  adhere  to  the  wall  if  brick  having  a  good 
suction  are  used  on  the  inside  and  the  mortar  joints  are 
raked  out  so  as  to  allow  the  plaster  to  key  into  them. 

Concrete  walls  for  dryers  are  without  question,  a  failure. 
True,  they  will  hold  up  the  roof  and  prevent  all  of  the  heat 
from  getting  away,  but  on  actual  tests  they  have  proved 


46       Clay  Plant  Construction  and  Operation 

themselves  to  be  poor  insulators.  In  comparing  the  fuel 
consumption  of  the  outside  tunnels  of  two  radiation  dryers, 
one  having  twelve-inch  walls  of  brick  and  the  other  twelve- 
inch  walls  of  concrete,  the  concrete  dryer  showed  a  fuel 
consumption  thirty  per  cent,  higher  than  the  brick  dryer. 
Both  dryers  were  identical  except  for  the  material  in  the 
walls  and  were  drying  the  same  ware.  If  it  were  possible 
to  build  comparatively  thin  concrete  walls  with  an  air  space, 
the  difficulty  might  be  overcome,  but  while  this  is  possible 
it  is  not  practical. 

Hollow-tile  is  the  ideal  material  for  dryer  walls.  It  not 
only  has  all  the  strength  necessary,  but  the  cells  provide  the 
necessary  air  spaces  and  the  tile  are  usually  scored  for 
plaster.  It  is  not  necessary  to  use  No.  1  tile  for  this  type  of 
building  as  it  is  always  possible  to  buy  good  seconds,  if  the 
clayworker  does  not  manufacture  tile  himself,  which  will 
make  an  excellent  job.  When  a  tile  wall  is  used  it  should  be 
twelve  inches  thick  and  it  is  equally  as  important  to  plaster 
it  as  in  the  case  of  a  brick  wall. 

Where  dryer  walls  (not  footings)  extend  below  grade  in 
order  to  protect  flues,  as  is  the  case  in  radiation  dryers  and 
some  waste  heat  and  steam  dryers,  it  is  very  necessary 
to  have  them  absolutely  waterproof.  Due  to  the  rapid 
evaporation  on  the  inside  of  such  walls,  the  amount  of 
moisture  drawn  thru  them  is  very  great.  This  is  generally 
made  worse  by  the  fact  that  eaves-troughs  are  seldom  pro- 
vided for  the  dryer  buildings.  The  effect  of  moisture,  and 
the  radiation  from  outside  walls  combined,  often  decrease 
the  efficiency  of  outside  tunnels  by  one-half. 

The  walls  below  grade  should  be  plastered  on  the  outside 
with  a  mixture  consisting  of  two  parts  sand  and  one  of 
cement,  which,  after  setting,  should  be  given  a  good  coat  of 
tar.  It  should  be  borne  in  mind  that  this  waterproofing  be- 
low grade  is  as  important  as  insulation  above  grade. 

DRAINAGE 

4 

Clay  workers  have  become  pretty  well  convinced  of  late 
that  drainage  of  kiln  bottoms  is  an  absolute  necessity,  but 
not  one  in  a  hundred  gives  the  dryer  a  thought  in  this  con- 
nection. 

Waste  heat  and  radiation  dryers  are  the  types  that  suffer 
most  in  this  respect.  Waste  heat  flues  and  the  under  flues 
of  the  dryer  building  are  more  often  than  not,  saturated 


Dryer  Details  47 

with  moisture  during  and  after  a  wet  spell.  Moreover,  it  is 
a  common  thing  to  find  a  waste  heat  flue  deliberately  used 
as  a  drain  for  the  surface  water  of  a  yard.  What  sort  of 
dryer  efficiency  can  a  clayworker  c.vpcct  who  deliberately 
Puts  moisture  from  outside  sources  into  a  building  which  is 
designed  to  extract  and  conduct  away  moisture  from  the 
ware  put  into  it?  There  are  some  instances  where  it  may 
not  be  possible  to  keep  water  out  of  the  flues,  but  in  most 
cases  there  is  no  excuse  for  its  presence. 

Waste  heat  flues  should  be  drained  in  exactly  the  same 
manner  as  kiln  bottoms,  that  is,  by  running  drains  under 
them  and  by  draining  surface  water  away  from  them. 

The  under-flue  system  of  a  dryer,  whatever  the  type, 
should  be  underlaid  with  a  series  of  drains  that  will  con- 
duct away  every  particle  of  moisture  possible. 

It  is  not  uncommon  to  see  plants  on  which  the  kiln  bot- 
toms are  so  well  drained  that  they  are  always  dry,  but  on 
which  not  the  least  precaution  has  been  taken  to  drain  the 
dryer  and  its  flues.  The  result  is  that  it  is  an  impossi- 
bility to  get  dry  ware  during  a  wet  spell,  no  matter  how 
much  fuel  is  used  on  the  auxiliary  heaters,  and  right  there 
is  a  point.  Does  the  average  clayworker  stop  to  figure  why 
he  uses  so  much  more  fuel  in  the  auxiliary  heater  or  else 
get  so  much  more  wet  ware,  in  the  spring,  winter  and  fall? 
There  is  but  one  answer  to  that  question  and  that  is,  mois- 
ture in  the  flue  system. 


CHAPTER  V 


Dryer  Construction 


JV/TANY  DRYERS  which  are  otherwise  well  built  have 
****•  their. efficiency  greatly  reduced  thru  having  a  poor 
roof.  It  is  utter  folly  to  expect  a  reinforced  concrete  or 
steel  and  brick  roof  from  three  to  four  inches  in  thickness 
to  prevent  excessive  radiation  and  to  keep  out  moisture. 
It  is  exactly  the  same  proposition  as  building  a  kiln  with 
a  three-foot  wall  to  prevent  radiation  and  then  covering 
it  with  a  nine-inch  crown.  Any  clayworker  who  has  put 
a  second  story  over  his  dryer  tunnels  and  used  it  for 
drying  purposes  knows  this  from  the  fact  that  he  can 
dry  in  the  upper  story  almost  as  well  as  in  the  tunnels 
simply  from  the  radiation  thru  the  dryer  roof.  Further- 
more, such  a  roof  should  be  protected  from  the  rain  and 
snow  by  a  protecting  roof,  otherwise  a  very  large  per- 
centage of  the  moisture  from  this  source  is  certain  to 
find  its  way  into  the  tunnels. 

If  it  is  proposed  at  some  future  time  to  put  a  second  story 
over  the  tunnels  in  order  to  increase  the  drying  capacity,  as 
is  often  done  on  hollow-ware  plants,  a  thin,  solid  roof  over 
the  tunnels  is  the  proper  construction,  but  if  such  is  not  the 
case,  every  effort  should  be  made  to  so  construct  a  roof  that 
practically  all  radiation  is  prevented. 

A  roof  which  has  been  designed  from  the  results  of  thoro 
laboratory  experiments  and  is  practically  the  last  word  in 
dryer  roof  design  is  shown  in  Fig.  20.  As  will  be  seen,  it 
consists  of  two  courses  of  four-cell  six-inch  hollow-tile  with 
a  layer  of  insulating  felt  between.  The  under  side  is  given 
a  coat  of  ^4-inch  cement  stucco  mixed  very  lean  and  the  top 
is  coated  with  one  inch  of  cinder  concrete.  Such  a  roof  is 
unquestionably  more  expensive  than  the  ordinary  dryer  roof, 
but  its  efficiency  will  soon  pay  any  additional  cost.  The  tile 
are  supported  on  "T"  irons  spaced  one-foot  centers.  This  ~oof 
is  a  decided  success  in  preventing  radiation  and  its  construc- 

48 


Dryer  Construction 


49 


50       Clay  Plant  Construction  and  Operation 

tkm  might  well  be  copied.    While  a  roof  of  four-inch  parti- 
tion or  book  tile  is  fairly  good,  it  is  too  thin  to  be  efficient. 

RAILS 

In  considering  the  dryer  it  would  hardly  do  to  pass  by 
without  devoting  some  space  to  track  construction.  Put- 
ting cars  on  the  track  in  hot  tunnels  is  the  curse  of  many 
plants,  and  strange  as  it  may  seem,  no  real  efforts  are  ever 
made  to  permanently  overcome  the  trouble.  Many  claywork- 
ers  would  not  credit  the  statement  that  there  are  some  plants 
that  have  operated  for  years  and  have  never  had  a  dryer  car 
jump  the  track  in  a  tunnel,  yet  such  is  the  case.  It  is  simply 
another  case  of  engineering  methods  against  "any  old  way." 

The  atmosphere  in  a  dryer  is  such  that  wooden  ties  will  not 
hold  spikes  for  any  length  of  time.  The  moisture  and  heat 
combined  tend  to  shrink  and  rot  any  kind  of  timber.  Also 
there  is  the  constant  danger  in  many  dryers  of  the  ties  catch- 
ing fire. 

The  most  modern  method  of  overcoming  these  difficulties 


Fig.   21.     Cast    Iron    Rail    Clamp. 

is  to  use  steel  rails  for  ties.  These  rails  are  built  into  the 
dryer  walls  and  are  therefore  stationary.  The  tracks  are  laid 
on  these  rail  ties  and  fastened  to  them  with  cast  iron  rail 
clamps,  as  shown  in  Fig.  31.  Dryer  tracks  constructed  in 


Dryer  Construction  51 

this  way  will  be  trouble-proof.  Fig.  22  illustrates  this  method 
of  construction. 

The  rails  in  dryers  are  very  often  too  light  for  the  work 
expected  of  them.  Twenty  to  twenty-five  pound  rails  will  do 
much  toward  eliminating  trouble,  as  there  is  no  chance  of 
their  kinking  under  the  weight  they  have  to  carry. 

The  grade  or  fall  given  the  tracks  in  a  dryer  is  an  impor- 
tant item.  It  should  be  only  just  enough  so  that  the  transfer 
men  are  compelled  to  push  a  car  without  any  great  effort, 
all  the  way  into  a  tunnel,  or  to  pull  a  car  out  without  having 
the  cars  behind  rush  out  before  giving  a  chance  to  block 
them.  When  too  much  grade  is  given  the  men  will  "shoot" 
a  car  into  a  tunnel  with  the  result  that  when  the  moving  car 
hits  the  stationary  ones  considerable  ware  is  broken  or  dam- 
aged all  the  way  down  the  line,  to  say  nothing  of  the  mess 
created  on  the  tracks.  Too  little,  fall  is  also  bad,  for  in  that 
case  the  line  of  cars  cannot  be  started  without  "bumping" 
them  in  much  the  same  way  that  a  locomotive  takes  up 
slack  for  a  start.  This  results  also  in  much  damaged  ware. 

A  grade  of  one  foot  in  one  hundred  has  proved  to  be  good 
for  the  average  dryer,  altho  with  cars  which  run  easily,  this 
has  sometimes  been  a  little  too  much,  and  with  hard  running 
cars  too  little. 

TUNNEL    DIMENSIONS 

In  an  open  room  dryer  the  dimensions  are  not  very  im- 
portant, the  main  point  to  be  watched  being  the  keeping  of 
the  source  of  heat  below  the  ware. 

In  tunnel  dryers  where  the  flow  of  heat  is  horizontal  or 
partially  so,  the  dimensions  of  the  tunnels  are  extremely  im- 
portant. If  there  is  any  one  thing  that  makes  for  inefficiency 
in  many  dryers  it  is  the  overlooking  of  this  fact.  In  order 
that  the  heat  in  a  tunnel  may  do  efficient  work,  the  car  and 
ware  must  fit  as  tight  as  is  practically  possible.  Space  over 
the  top  of  the  ware  should  be  absolutely  avoided,  for  heated 
air  always  rises  to  the  top,  and  if  it  is  given  an  opportunity, 
most  of  it  will  flow  over  the  top  of  the  ware  instead  of  around 
and  thru  it.  Not  only  is  heat  wasted  in  this  manner  but  the 
top  courses  of  ware  are  dried  first  and  often  too  fast  with 
heavy  losses  as  a  result.  In  building  tunnels  it  is  therefore 
absolutely  necessary  that  the  exact  height  of  a  loaded  car  of 
ware  be  known  and  only  sufficient  space  left  above  to  give 
clearance. 

On  each  side  of  the  cars  also  only  sufficient  space  should 


52  Clay  Plant  Construction  and  Operation 


Dryer  Construction  58 

be  left  to  give  good  clearance,  otherwise  the  air  will  take 
the  path  of  least  resistance  and  a  large  proportion  of  it  will 
flow  between  car  and  walls  without  doing  any  work. 

The  design  of  the  lower  part  of  the  tunnels  is  an  item 
which  is  overlooked  by  nearly  all  dryer  constructors.  Even 
those  who  make  the  cars  fit  tight  in  a  tunnel  give  very  little 
thought  to  the  creation  of  a  flow  of  air  beneath  the  cars  or 
to  the  getting  rid  of  the  ware  which  is  jarred  or  falls  from 
the  cars,  and  which  in  the  average  dryer  is  the  cause  of  so 
many  cars  jumping  the  track. 

If  steel  rail  ties  are  used  to  support  the  tracks  it  is  a  simple 
matter  to  leave  a  space  of  one  foot  below  the  tracks  the 
full  length  of  the  tunnels.  This  space  offers  a  free  path  for 
the  air  flowing  thru  the  tunnel  which,  combined  with  the 
natural  tendency  of  the  air  to  rise,  gives  exactly  the  condi- 
tion in  the  tunnel  which  is  most  desired,  namely,  a  circula- 
tion thru  and  under  the- ware. 

Furthermore,  this  space  allows  all  ware  falling  from  the 
cars  to  accumulate  under  the  tracks  instead  of  on  them.  Even 
in  dryers  where  there  is  much  loss  during  transit  thru  the 
tunnels  this  space  will  only  require  cleaning  out  about  once 
each  year.  Most  clayworkers  who  have  had  experience  with 
tunnel  dryers  will  undoubtedly  agree  that  if  the  space  serves 
no  other  purpose,  the  fact  that  it  will  keep  the  tracks  clean 
makes  it  a  really  worth  while  item  in  dryer  design.  This  type 
of  construction  is  also  shown  in  Fig.  22. 

The  question  of  putting  one  or  two  tracks  in  a  tunnel  often 
comes  to  the  fore.  There  can  be  no  question  that  it  is  an 
extremely  annoying  thing  to  have  a  loaded  car  jump  the 
track  in  a  single  tunnel  dryer,  especially  where  the  cars  fit 
fairly  tight.  Sometimes  the  cars  will  be  in  such  a  position 
that,  due  to  the  limited  space  in  which  the  men  have  to  work, 
it  takes  hours  to  get  it  on  again.  Much  of  this  trouble  is 
eliminated  when  double  track  tunnels  are  built,  for  by  tem- 
porarily clearing  one  track,  plenty  of  room  is  provided  for 
several  men  to  get  around  the  wrecked  car.  A  well  designed 
double  track  dryer  should  be  as  efficient  as  a  single  track 
dryer  and  the  advantage  referred  to  above  should  carry 
weight  when  considering  this  question.  It  is  also  cheaper  to 
construct. 

DOORS 

A  vexing  dryer  problem  is  that  of  doors.  Any  number  of 
different  designs  are  in  use,  but  each  one  of  them  seems  to 


54       Clay  Plant  Construction  and  Operation 


leave  something  to  be  desired.  For  single  tunnels  a  pair  of 
small  outward  swinging  sheet  steel  doors  to  each  tunnel  is 
much  in  favor.  Having  two  doors  to  each  tunnel  makes  each 
of -them  very  light,'  and  as  they  swing  out,  a  string  of  cars 
that  may  be  accidentally  started  will  part  and  pass  thru  them 


Fig.   23.     Double   Steel    Doors. 

without  doing  them  injury.  Such  a  pair  of  doors  is  illus- 
trated in  Fig.  23.  The  space  between  the  rails,  which  is  often 
left  so  that  it  admits  much  cold  air,  can  be  filled  with  a  2x4 
with  grooves  cut  for  the  wheel  flanges.  Where  double  tun- 
nels are  used  the  swinging  steel  door  is  not  so  successful  as 
its  weight  is  inclined  to  make  it  sag,  thus  causing  trouble  in 
dragging  on  the  rails  when  opening  or  closing. 

The  .counterbalanced  door  which  is  raised  and  lowered  is 
a  popular  type,  especially  where  the  storage  space  at  the  co.ol 
and  hot. ends  is  limited,  but  it  has  the  disadvantage  of  being 
battered  or  broken  if  the  cars  in  the  tunnel  start  and  jamb  it. 

Another  type  which  is  less  popular,  but  nevertheless  suc- 
cessful, is  the  sheet  steel  door  with  the  hinge  at  the  top.  This 
is  swung,  open  by  lifting  from  the  bottom.  Cars  striking  it 
merely  lift  it  without  doing  it  any  damage.  However,  for 
double  tunnels  it  is  quite  heavy  and  this  is  a  disadvantage, 


Dryer  Construction 


55 


altho  it  can  be  counterweighed.  This  door  can  be  fitted  tight 
around  the  rails.  Suspended  hooks  must  be  provided  for 
holding  it  open  while  putting  in  or  drawing  cars.  This  type 
of  door  is  shown  in  Fig.  24. 

VENT    STACK    CONSTRUCTION 

Many  dryers,  both  of  the  tunnel  and  open  room  type  are 
provided  with  a  stack  at  the  cool  end.  This  acts  in  lieu  of 
an  exhaust  fan.  The  question  as  to  whether  to  use  a  fan  or 
a  stack  is  one  that  can  only  be  decided  by  an  engineer  who 
has  examined  the  proposition  thoroly,  but  there  is  this  to  be 
said  in  favor  of  the  stack — it  does  away  with  the  fixed  opera- 
ting charge  of  a  fan. 

Vent  stacks  are  often  built  of  lumber,  but  when  built  in 
this  way  they  are  not  a  good,  permanent  investment.  Stacks 
of  brick  or  hollow-tile  when  well  built  are  both  permanent 
and  of  good  appearance.  This  latter  point  is  worth  considera- 
tion at  this  time  when  all  industries  seem  to  be  vicing  with 
each  other  in  their  efforts  to  combine  utility  with  beauty  in 
factory  buildings. 


ffi 


Fig.    24.     Steel     Moving    Doors    for    Double    Track    Tunnels. 

When  building  of  brick  or  tile,  the  walls  of  the  stack  should 
be  8y2  inches  thick.  As  a  vent  stack  for  a  ten-tunnel  dryer 
or  its  equivalent  in  width  offers  a  fairly  large  surface  to  the 
wind,  it  is  safest  to  use  cement  mortar  or  at  least  a  well 
spiked  lime  mortar. 

On  account  of  the  varying  and  fluctuating  temperatures  of 
the  vapors  from  a  dryer,  it  is  difficult  to  figure  a  dryer  stack 


56       Clay  Plant  Construction  and  Operation 


i      aiM^t-E  TUMMKL.&  X[ 

A-3"   1    BtAM» 


U/a  TKACK 


A  ~  6'  I    SEAMS 


ivfc    TKACK  T»JM^< 


Fig.   25.     Betall    of 


Dryer  Construction 
'. 


TnESC      DIMENSIONS 
DouSutD      Fog. 
TEN   TRACKS 


Brick    Dryer    Stack. 


58       Clay  Plant  Construction  and  Operation 

m 

as  is  done  in  the  case  of  a  boiler  stack.  It  has,  therefore, 
become  an  almost  general  practice  to  build  these  stacks  fifty 
feet  high.  If  it  should  be  necessary  to  build  a  higher  stack 
than  this,  it  is  a  question  whether  it  would  not  be  better  to 
install  a  fan  in  the  beginning. 

When  constructing  a  stack,  consideration  must  be  given  to 
the  fact  that  it  must  span  the  tunnels  or  rooms.  This  means 
that  the  walls  between  the  tunnels  or  rooms  directly  under 
the  stack  must  carry  concentrated  loads.  Also  that  the  stack 
walls  directly  over  the  tunnels  must  be  carried  on  steel. 

Fig.  25  shows  a  standard  type  of  stack  for  a  ten-track  dryer 
having  one  track  in  each  tunnel.  When  built  of  brick  this 
stack  weighs  approximately  ninety  tons.  Including  the  two 
outside  walls  this  means  that  each  of  the  eleven  walls  must 
be  figured  so  that  they  will  safely  carry  this  load.  The 
area  of  the  foundation  will  naturally  depend  upon  the  na- 
ture of  the  soil  upon  which  they  are  built.  The  walls  sup- 
porting the  stack  should  be  laid  up  in  cement  mortar.  Sev- 
eral collapses  have  occurred  which  have  caused  much  damage 
to  buildings  thru  lack  of  attention  to  these  details,  and  it  will 
pay  well  to  give  them  close  attention. 

In  single  track  tunnel  dryers  two  three-inch  "I"  beams  un- 
der each  wall  will  safely  carry  the  load,  as  each  span  is  short. 
In  double  track  tunnel  dryers  two  six-inch  "I"  beams  should 
be  used  under  each  wall.  When  a  ten-track  dryer  is  divided 
into  two  rooms  and  the  steel  must  span  five  tracks,  four  ten- 
inch  "I"  beams  are' required  to  carry  the  load,  two  under  each 
wall. 

In  cases  where  it  is  desired  to  put  ten  tracks  in  one  large 
room  it  is  necessary  to  build  a  pier  eighteen  inches  square  in 
the  center  of  the  span,  which  of  course,  makes  the  construc- 
tion the  same  as  for  a  five-track  span. 

STORAGE  AND  COOLING  TRACKS 

Few  clayworkers  who  are  not  fortunate  enough  to  have 
had  experience  with  a  liberal  storage  space  at  each  end  of 
the  dryer  fully  realize  the  value  of  it.  Dryers  are  often 
encountered  which  have  no  storage  room  at  all  at  the  cool 
end  and  probably  room  for  only  one  car  at  the  hot  end.  ^nd 
this,  in  spite  of  the  fact  that  plenty  of  space  was -available 
at  the  time,  the  dryers  were  built. 

It  is  always  advisable  to  have  storage  room  for  at  least 
three  cars  on  each  track  at  the  cool  end  and  from  three  to 
five  cars  at  the  hot  end.  The  storage  at  the  cool  end  allows 


Dryer  Construction 


59 


for  fluctuations  in  the  speed  of  the  setters,  also  for  occasions 
when  damp  ware  begins  to  show  at  the  hot  end  and- setting 
must  be  stopped,  as  is  the  case  on  many  plants  late  in. the 
afternoon.  With  a  storage, 'the  machine  can  keep  running  on 
extra  cars  which  can  be  thrown  in  on  the  storage  tracks  be- 


WOOD    PLUG 


Tuftg- 


Fig.    26.     Detail    of    Post    for    Drying    Shed. 

fore   each   tunnel  and   put  into  the   dryer  during  the  night 
when  dry  cars  can  be  pulled. 

A.  good  storage  at  the  not  end  allows  me  transfer  men  to 
/nake  a  pull  of  several  cars  from  each  tunnel  at  a  time,  thus 
saving  time  and  cutting  down  labor  costs.  The  ware  gets 


60       Clay  Plant  Construction  and  Operation 

sufficient  time  to  cool,  and  is  therefore,  handled  more  care- 
fully by  the  setting  crew.  An  important  point  to  be  consid- 
ered also  is  that  if  extra  cars  are  provided  the  capacity  of 
the  dryer  can  be  materially  increased.  With  the  dryer  full 
and  two  or  three  full  cars  on  each  storage  track  at  the  cool 
end  at  quitting  time,  it  is  very  little  trouble  for  the  night 
burners  to  make  one,  two  or  three  pulls  during  the  night  and 
at  the  same  time  put  the  wet  cars  in  as  room  is  made  for 
them.  This  system  will  often  get  that  little  extra  capacity 
out  of  a  dryer  which  is  needed  to  keep  it  in  step  with  the 
machine  and  kilns  and,  at  the  same  time,  get  all  dry  ware. 

The  storage  tracks  should  always  be  provided  with  a  roof 
as  much  of  their  value  is  lost  if  this  is  not  done. 

A  very  neat  method  of  supporting  such  a  roof  is  shown 
in  Fig.  26.  These  supports  are  made  of  used  four-inch  boiler 
tubes  or  four-inch  pipe  and  the  braces  of  used  two-inch  pipe. 
When  given  a  coat  of  paint  they  are  not  only  neat  but  are 
exceedingly  strong  and  take  up  less  room  between  the  tracks 
tha*  almost  any  other  type  of  construction. 


CHAPTER  VI 


Setting  Up-Draft  Kilns 

O  ETTING  BRICK  in  up-draft  kilns  is  a  more  complicated 
^  process  than  setting  in  down-drafts,  and  it  is  reason- 
ably safe  to  say  that  there  are  far  more  methods  of  setting 
the  former  type  than  in  the  latter.  Of  these  many  meth- 
ods, there  is  one  that  has  found  very  little  use  in  the 
United  States,  altho  its  many  good  points  should  com- 
mend it  to  the  clayworker.  This  is  known  as  the  "tight 
bolt"  method.  When  used  in  down-draft  kilns,  it  is  the 
simplest  and  fastest  of  all  methods,  and  produces  most 
excellent  results. 

The  same  can  be  said  of  this  method  for  up-draft  kilns, 
but  on  account  of  the  necessity  of  setting  arches  and 
loose  heads,  as  in  all  up-draft  setting,  the  setters  must  be 
skilled  men. 

The  good  points  in  favor  of  this  method  are  that,  in  that 
part  of  the  kiln  where  the  bolts  are  set,  the  brick  are  of 
more  even  shade;  the  setting  is  accomplished  at  a  faster 
rate;  the  faces  of  the  brick  are  a  plain,  even,  unflashed 
olor,  and  there  is  absolutely  no  kiln  marking.  Also,  if 
;he  firing  is  done  under  occasional  reducing  conditions, 
the  faces  of  the  brick  will  show  a  red  heart  with  brown 
or  black  ring — a  much  sought-after  result. 

As  will  be  seen  from  the  accompanying  drawings,  the 
legs  of  the  arches  are  set  three  brick  wide,  a  general  cus- 
tom in  this  type  of  kiln  (up-draft).  The  brick  in  the  cen- 
ter of  the  leg  are  set  tight,  while  those  on  the  outside  are 
set  as  open  as  possible.  When  the  overhangers  are 
reached,  they  are  set  in  tight  and  open  courses,  as  shown, 
and  between  them  the  brick  are  set  in  regular  tight-bolts. 
Above  the  brick  which  close  the  top  of  the  arches  an 
open  course  is  set.  This  course  should  be  very  open,  in 
fact,  as  open  as  possible  and  still  prevent  the  brick  above 
from  breaking  under  the  load. 

61 


62       Clay  Plant  Construction  and  Operation 

Above  this  course  the  "tight  bolts  oegin  and  are  car- 
ried up  to  within  six  courses  from  the  top  of  the  kiln. 

"Tight  bolts"  consist  merely  of  an  absolutely  tight 
bench  of  brick.  In  looking  at  this  bench  it  presents  a 
solid  face  of  headers.  Each  bench  is  set  one  inch  from 
the  one  behind,  this  one-inch  space  being  left  for  the 


travel  of  the  fire  gases.  In  order  to  maintain  this  dis- 
tance a  "follow  board"  is  used.  This  is  a  one-inch  board 
with  a  couple  or  more  leather  handles  on  the  top  edge. 
As  the  bench  is  carried  up,  the  board  is  drawn  up  and  al- 


Setting  Up-Draft  Kilns  03 

lowed  to  rest  on  a  few  brick  shoved  back  from  the  Jbench 
which  is  being  set.  In. order  to  prevent" the  benches  from 
rolling,  every  fourth  or  fifth  brick  in  every  fourth  or  fifth 
course  is  shoved  back  until  it  touches  the  bench  behind. 
This  makes  the  setting  perfectly  stable.  Care  must  be 
taken,  of  course,  to -carry  up  the  benches  perfectly  straight. 

FACILITATES    HANDLING   OF    BRICK 

In  this  method  of  setting  the  setter  can  pick  up  from  the 
car  or  barrow  all  the  brick  he  can  hold  between  his  two 
hands,  drop  them  on  the  bench  and  push  them  back  against 


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Fig.  28.  Cross-Section  of  Kiln  Showing  Again  How  Platting 
is  Laid  and  the  Loose  Setting  of  the  Outside  Brick  in  the  Arch 
Legs.  This  Drawina  Also  Shows  the  Solid  Face  of  Headers 
Present  by  a  Bench  of  "Tight  Bolts." 


the  follow  board.  It  is  exactly  the  same  as  taking  burned 
brick  from  the  barrow  and  placing  them  on  a  hack. 

The  brick  should  be  set  loose  next  to  the  walls  in  order 
to  pull  the  heat  to  this  usually  backward  part  of  the  kiln. 

The  six  top  courses  should  be  set  three  on  one  and  on 
top  of  this  the  platting  is  handled  in  the  usual  manner. 

Upon    first    looking    at    a   kiln    set    with    "tight   bolts"    the 


64       Clay  Plant  Construction  and  Operation 

average  plant  manager  or  superintendent  would  pronounce 
it  "impossible."  It  is,  however,  used  with  great  success  in 
some  sections  of  the  country,  and  where  this  method  of  set- 
ting is  followed,  it  would  be  utterly  impossible  to  persuade 
the  clayworkers  to  change  to  any  other  method.  The  aver- 
age recovery  of  No.  1  face-brick  from  up-draft  kilns  set 
in  this  way  is  well  over  fifty  per  cent,  and  this  in  districts 
where  the  brick  must  compete  with  the  output  of  modern 
continuous  and  down-draft  kilns. 


CHAPTER  VII 


Setting  Down-Draft  Kilns 


SETTING  THE  KILN,  or,  to  more  properly  state  it,  set- 
ting the  ware  in  the  kiln,  has  been  a  subject  for  study 
and  experiment  ever  since  the  first  kiln  was  built — or  rather, 
ever  since  the  first  kiln  was  set.  It  has  grown  in  importance 
as  kiln  structures  developed,  and,  within  the  past  decade  has 
become  a  matter  of  vital  importance. 


Fig.  29.     Showing  Method  of  Raising  Heads. 


This  is  due,  in  great  measure,  to  the  introduction  of  tex- 
ture face-brick,  for,  fast  following  the  early  popularity  of 
this  material,  hundreds  of  plants  which  had  never  before 
attempted  the  manufacture  of  anything  but  commons,  be- 
came— at  least  partially — face-brick  producers. 

In  the  production  of  common-brick,  the  manner  of 
setting  was  of  little  moment,  so  long  as  it  insured  a  firm 
mass,  frequent  draft-passages  and  kiln  capacity.  But  in 

65 


66       Clay  Plant  Construction  and  Operation 

order  to  secure  good,  merchantable  face-brick,  these  manu- 
facturers found  it  necessary  to  make  radical  changes  in 
their  setting  methods — finding,  indeed,  that  setting  the 
kiln  was  fully  as  important  as  any  of  the  preliminary  pro- 
cesses of  manufacture,  and  as  the  actual  burning. 

Nor  is  the  interest  confined  to  those  brickmakers  who 
have  turned  a  part  of  their  output  from  common-  to  face- 
brick,  for  many  plants,  hitherto  exclusively  devoted  to  the 
manufacture  of  smooth  faced  face-brick,  have  found  that 
the  introduction  of  the  new  matt  surfaced  product  had  a 
way  of  reversing  old  rules,  and  so  these  brickmakers  were 
called  upon  to  invent  or  adopt  new  ones. 

The  above,  of  course,  refers  entirely  to  the  effect  of 
the  setting  upon  the  appearance  of  the  finished  product. 
Another  important  item  must  be  considered — the  relation 
between  the  setting  and  the  efficient  operation  of  the  kiln. 
Kiln  designers,  some  time  ago,  found  that  they  could 
not  successfully  use  the  rules  laid  down  for  ordinary  metal- 
lurgical furnace  construction,  because  in  considering  fire- 
box area,  flue  area  and  stack  area  and  height,  they  must 
always  figure  on  the  dense  checker  work  thru  which 

the  gases  have  to  travel, 
downward,  aided  only 
by  natural  draft.  Of  ne- 
cessity they  worked  out 
rules  and  ratios  of  their 
own,  and  in  these  rules 
and  ratios  the  setting 
was  taken  fully  into 
consideration.  In  a  well 
designed,  up-to-the- 
minute-kiln,  therefore, 

Fig.  30.  Plan  of  "Herring  Bone"  the  method  or  density 
and  Skintle  Course.  All  Brick  Set  of  the  setting  makes 
on  Edge.  ,.  ,  ,.„ 

very     little     difference, 

but  there  are  thous- 
ands of  kilns  where  it  makes  all  the  difference  between 
success  and  failure. 

EFFECT   OF    SETTING    ON    BURNING 

In  the  first  place  the  setting  will  be  considered  only 
from  the  standpoint  of  its  effect  on  the  operation  of  the 
kiln. 

As  a  general  rule,  the  setting  of  the  ware  has  a  greater 
effect  in  a  round  kiln  than  in  a  rectangular  one.  This 


Setting  Down-Draft  Kilns 


67 


is  due  to  the  fact  that  in  the  majority  of  round  kilns  the 
fire  gases  are  compelled  to  travel  about  twice  the  distance 


Fig.    31. — Front    Elevation.      Single    Header 
and  Stretcher. 


nnnnnn 


from  the  fire-boxes  to  the  center,  as  in  a  rectangular  kiln. 
There  is,  then,  far  more  opportunity  for  the  gases  to 
"short  exit"  into  the  flues  and  leave  a  cone  of  soft  brick  in 
the  center,  and  this  is  exactly  what  happens  in  very  many 
cases.  The  remedy  is  very  simple — the  benches  should  be 
tightened  (brick  set  closer  together)  near  the  bag-walls 
and  gradually  loosened  as  the  middle  of  the  kiln  is  ap- 
proached. 

When  this  trouble  occurs  in  a  rectangular  kiln  the  same 
remedy  will  overcome  it.  The  effect  of  this  is  to  baffle 
the  gases  near  the  fire-box  and  drive 
them  toward  the  center— they  naturally 
following  the  path  of  least  resist- 
ance. "Cool"  or  "hot"  spots  are  some- 
times found  to  recur  in  certain  places 
in  a  kiln.  When  such  spots  are  located, 
they  can  practically  always  be  elim- 
inated thru  changes  in  the  setting.  In 
the  case  of  a  "cool"  spot,  the  setting 
should  be  "opened  up"  in  order  that 
more  of  the  fire  gases  may  be  drawn 
to  that  particular  point.  A  "hot"  spot 
is  treated  in  the  opposite  manner — the 
brick  are  set  tighter  at  his  point  in 
order  that  less  of  the  fire  gases  may 
pass  thru  it. 

The  tightness  or  looseness  of  the  setting — (these  terms  are 
used  to   designate  the   distance  the  brick  are  set  from  each 


II II  II II II 


II H I  Illl 


II II II II II 


d 


UUUUULJ 


Fig.  32.  Section 
Thru    Bench. 


68       Clay  Plant  Construction  and  Operation 

other)  has  a  very  great  effect  on  the  burning  qualities  of 
many  kilns.  By  setting  too  tight,  in  an  effort  to  crowd  a 
large  number  of  brick  into  a  kiln,  the  burning  period  is  length- 
ened out  of  all  proportion  to  the  gain  in  holding  capacity. 
The  draft  is  cut  to  such  an  extent  that  "water  settles"  and 
"black  cores"  develop;  the  fuel  consumption  is  unreasonably 
high,  due  to  the  length  of  the  burn;  overburned  brick  on  the 
top,  and  underburned  brick  in  the  bottom  are  the  rule.  On 
the  other  hand,  where  the  setting  is  too  open,  space  is  lost 
that  is  valuable,  and  considerable  of  the  heat  value  of  the 
fuel  is  wasted  thru  escaping  too  readily  to  the  stack. 

These  things  must  be  taken  into  serious  consideration 
by  the  clayworker  who  would  bring  his  plant  to  the 
highest  point  of  efficiency. 

EFFECT  OF  SETTING  ON   PRODUCTS 

The  setting  of  brick  in  the  kiln  is  an  all  important  fac- 
tor in  the  quality  of  the  finished  product.  It  determines 
whether,  under  certain  burning  conditions,  the  face  of 
the  product  will  be  of  a  clear  color  or  flashed,  and  whether 
the  flash  covers  part  or  all  of  the  face.  It  also  determines 
to  a  great  extent  how  much  of  the  ware  will  be  marked 
in  the  burning.  Just  what  methods  are  used  to  obtain  the 
various  results  will  be  taken  up  in  detail  later. 

SKILLED  LABOR 

There  is  probably  no  other  department  in  a  brick  plant 
where  as  highly  skilled  labor  is  required  as  in  the  setting 
department.  Setters  must  handle  the  brick  rapidly  and 
carefully,  at  a  stage  when  these  brick  are  more  susceptible 
to  damage  than  at  any  other.  A  great  deal  of  a  burners' 
troyble  in  having  kilns  "roll"  or  heads  pulled  into  the 
fires,  is  properly  chargeable  to  faults  in  the  setting.  Very 
often  the  blame  is  never  placed  where  it  belongs  and  the 
burner  struggles  along  under  a  handicap  he  is  unable  to  over- 
come. 

A  skilled  setter  should  constantly  keep  in  touch  with  his 
kilns  by  noting  results  as  they  are  emptied.  In  this  way  he 
can  often  suggest  improvements  and  can  most  certainly  cor- 
rect his  own  faults. 

HEIGHT  OF  SETTING 

Under  varying  conditions  brick  are  set  from  twenty- 
two  to  thirty-six  courses  high.  There  are  several  deter- 
mining factors  which  govern  the  height  to  which  brick 


Setting  Down-Draft  Kilns 


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70       Clay  Plant  Construction  and  Operation 

may  be  set.  Principal  among  these  are,  the  burning  quali- 
ties of  the  kiln;  the  ability  of  the  material  to  sustain  loads 
while  under  high  heats  and  the  liability  of  water  settles 
during  the  watersmoking  period. 


Fig.    35.     Showing    Double    Two    on    One,    Double    Three    on    One 
and    Double    Five    on    Two. 

In  almost  all  cases  the  kiln  determines  the  height  of 
the  setting.  A  clayworker  soon  finds  that  at  a  certain 
height  he  can  get  saleable  ware  in  the  bottom,  ana  in  a 
reasonable  burning  period.  Experience  also  teaches  him 
that  to  go  beyond  a  certain  point  means  overburned  tops 
in  spite  of  every  precaution. 

In  any  case,  sufficient  space  should  always  be  leit  be- 
tween the  top  of  the  setting  and  the  crown.  Consider- 
able combustion  takes  place  in  this  space,  due  to  un- 
burned  coal  gases  passing  into  the  kiln  and  there  mixing 
with  free  air.  When  combustion  space  is  not  allowed  for, 
these  gases  will  pass  thru  the  brick  in  an  unmixed  state, 
resulting  in  considerable  fuel  loss  and  a  longer  burning 
period  and  also  flashed  or  reduced  ware  when  it  may  not 
be  desired. 

In  some  lines  of  manufacture,  principally  fire-clay  shapes 
and  paving  block,  the  maximum  height  is  determined  by 
the  material.  At  high  temperatures  many  materials  will 
deform  when  too  heavily  loaded.  This  results  in  the  lower 
courses  being  "kiln  marked"  or  crushed. 

Kilns  with  poor  draft  are  sometimes  troubled  with 
water  settles  in  the  watersmoking  period.  These  are  caused 
by  the  ware  in  the  lower  courses  becoming  so  soft,  thru 
the  reabsorption  of  moisture  from  the  gases,  as  to  crush 
under  their  load.  About  the  only  remedy,  unless  changes 


Setting  Down-Draft  Kilns  71 

are  made  in  the  kiln  itself  or  the  method  of  burning,  is 
to  reduce  the  setting  height. 

As  a  general  rule  the  setting  is  "battered  back"  at  the 
tops  of  the  bag-  or  flash-walls,  altho  in  some  cases  a 
little  below.  It  is  seldom  good  practice  to  run  above  the 
bags  before  battering,  on  account  of  the  tendency  of  the 
fires  to  "pull"  the  brick  into  them.  Where  the  brick  are 
set  unusually  high,  the  upper  part  of  the  bag-wall  is  often 
built  of  checkerwork,  sometimes  laid  up  loose.  The  reason 
for  this  is  that  it  is  difficult  to  get  even  bottoms  in  some 
kilns  if  the  bag-walls  are  too  high.  In  such  cases  the 
checkerwork  at  the  top  acts  merely  as  a  brace  for  the 
setting,  while  not  interfering  with  the  burning. 

PREVENTING  SAGGING  OF  HEADS 

What  is  popularly  known  as  the  "pull  of  the  fires"  on 
the  setting  is  in  reality  not  "pull"  at  all.  It  is  due  to  the 
dilierence  in  tne  progression  of  the  shrinkage  between 
those  brick  close  to  the  fires  and  those  farther  away.  There 
is  a  difference  in  the  progression,  even  in  the  length  of  a 
single  brick,  as  the  head  of  the  brick  towards  the  fire  will 
start  shrinking  before  the  .head  that  is  away  from  the  fire. 
This  difference  multiplied  by  the  ten  or  fifteen  brick  of  the 
top  courses,  gives  a  decided  lean  towards  the  fire,  and  under 


Fig.     36. 


Method     of     Protecting     Heads 
from    Flash. 


certain    conditions    means    a    fire-box    full    of    brick.      This 
"tumbling"  is  often  brought  on  by  too  rapid  firing,  the  brick 
nearest  the  fires  naturally  catching  the  heat  first  and  shrink- 
ing  heavily  before   those   in  the   body  of   the  kiln. 
When     this     trouble     occurs     only     occasionally     and     at 


72       Clay  Plant  Construction  and  Operation 


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Setting  Down-Draft  Kilns  78 

isolated  furnaces,  the  commonest  method  of  prevent- 
ing a  "tumble"  is  to  temporarily  stop  firing  the  threatened 
furnace.  If  necessary,  the  fires  should  be  drawn  and  cold 
air  allowed  to  pass  thru  the  furnace  into  the  kiln.  This 
method  is  very  effective. 

In  cases  where  it  seems  practically  impossible  to  prevent 
"tumbling"  by  any  ordinary  "tying  in"  of  the  heads,  the 
following  methods  must  be  resorted  to:  Where  round 
kilns  are  used,  a  ring  three  or  four  stretchers  wide  is  set 
entirely  around  the  kiln,  close  up  to  the  bags.  This  ring 
is  generally  started  at  one  side  of  the  setting  door  and 
continued  around  the  kiln  to  the  other  side  of  the  dodr. 
The  floor  runners  or  brick  on  the  floor  are  set  so  as  to 
radiate  from  the  center  of  kiln.  All  of  the  headers  also 
radiate  in  the  same  way,  while  the  stretchers  run  in  circles. 
The  entire  ring  is  set  as  one  bench  and  is  securely  tied  to- 
gether by  the  stretchers.  When  the  top  of  the  bag-wall  is 
reached  the  batter  is  only  carried  up  two  or  three  courses  and 
headers  used  there  entirely.  With  extremely  troublesome 
materials,  two  rings,  one  inside  the  other,  are  sometimes  used. 
The  inside  ring  is  always  carried  up  higher  than  tlie  out- 
side. Inside  the  ring  or  rings,  the  regular  bench  setting  is 
used. 

The  author  has  never  known  of  a  case  where  this  ring 
setting,  if  properly  done,  has  not  eliminated  "tumbling."  It 
is,  of  course,  more  expensive  to  set  the  ring  than  the  bench 
on  account  of  the  extra  time  consumed. 

In  rectangular  kilns,  where  the  ring  method  is  impos- 
sible, the  benches  are  carried  up  as  usual  to  the  point 
where  the  trouble  is  encountered.  Strips  of  clay,  gener- 
ally made  from  waste  ends  from  the  cutter,  are  placed 
under  the  ends  of  the  stretchers  nearest  the  fire,  giving 
them  a  slope  towards  the  center  of  the  kiln.  This  is  shown 
in  Fig.  29.  In  most  cases,  this  need  only  be  done  on  one 
or  two  courses  to  make  it  effective. 

LAYING   OUT    BOTTOM    RUNNERS 

The  floor  runner  brick  should  always  be  set  to  conform 
to  the  type  of  bottom.  In  solid  bottom,  center  well,  round 
kilns  they  should  be  set  radially,  for  if  set  across  the  kiln, 
with  openings  between  for  draft  passage,  the  draft  will 
short  cut  to  the  center,  taking  the  path  of  least  resistance. 

In  checker  or  riddle  bottom  kilns,  the  runners  should 
be  set  so  as  not  to  interfere  with  the  floor  openings.  Many 


74       Clay  Plant  Construction  and  Operation 


kilns  work  badly  for  no  other  reason  than  that  no  atten- 
tion is  paid  by  the  setters  to  the  openings  in  the  floor. 
Very  often  the  erratic  action  of  a  kiln  is  due  to  this  one 
thing.  Setters  should  always  be  impressed  with  this  fact 
and  compelled  to  avoid  setting-  brick  over  the  openings. 
Kilns  are  often  so  located  that  the  top  portion  of  the 
kiln  must  be  wheeled  out  first,  leaving  the  "bottom"  until 
last.  This  "bottom"  may  consist  of  a  varying  number  of 
courses.  In  order  that  these  bottom  courses  may  be 
wheeled  over,  without  danger  of  their  "rolling"  under  the 
running  planks,  it  is  necessary  that  a  course  of  brick  be 
set  in  such  a  manner  as  to  make  a  firm  false  floor  or  wheel- 
ing course.  A  very  good  method  of  setting  this  "floor" 
is  illustrated  in  Fig.  30.  This  is  known  as  the  "herring 
bone  skintle."  One  course  only  is  set  in  this  manner,  the 
courses  below  and  above  it  being  set  in  the  regular  way. 

METHODS   OF   SETTING 

For  the  purposes  of  describing  them,  the  various  meth- 
ods of  setting  may  be  divided  as  follows:     Common-brick 


MUK       To      Dm.^<na.D      H«I«NT- 
A*     Ff»oM      CouM«e    I 


. ........  I 


J L 


FROUT     ff  I.KVAT  I  O»J  SECTion      Of      BtlNlcH 

Fig.  38.     Method  of  Setting  Whole   Kilns  on   Flat. 

setting;    unflashed    face-brick    setting;    flashed    face-brick 
setting  and  enameled-brick  setting. 

The    price    at    which    common-brick   is    sold   demands    that 
they    be    produced    as    cheaply    as    is    possible    and.    as    the 


Setting  Down-Draft  Kilns 


color  is  not  of  primary  importance  it  makes  very  little 
difference  whether  the  facets  flashed  or  unflashed.  The 
alternate  single  header  and  single  stretcher  fills  all  require- 
ments (Figs.  31  and  32).  It  is  quick  and  can  be  done 
by  setters  with  but  little  skill  and,  above  all,  it  is  a  very 


nnnon 


u 


uuuuuu 

Pl_Afsl     Of     CouWSB    II 


£-B~t  PL.AN   Of  COUHSKS    6-7 

8-=>-to 

Fig.  39.     Plan  Views  of  Settings  Shown   in  Fig.  38. 

stable  method.  The  question  as  to  whether  the  brick 
should  be  set  "two  on  one,"  "three  on  one"  or  "five  on 
one"  is  simply  one  of  kiln  draft  and  must  be  determined 
for  each  individual  case.  This  is  also  true  with  regard 
to  the  number  of  offsets  or  tie-courses  and  to  the  tieing 
in  of  the  heads. 

The  simplest  and  quickest  method  of  setting  common- 
brick  is  known  as  the  "tight  bolt"  method.  It  is  little 
known  in  the  United  States,  but  is  widely  used  in  England 
and  in  Canada,  in  both  up-  and  down-draft  kilns.  As  will 
be  seen,  in  Figs.  33  and  34,  the  brick  are  set  in  absolutely 
tight  benches,  all  headers,  running  from  bag-wall  to  bag- 
wall.  These  benches  are  set  approximately  one  inch  apart 
to  allow  for  draft  space  and  are  kept  from  "rolling"  by 
pushing  thru  an  occasional  brick  in  every  fourth  or  fifth 
course,  so  that  it  just  touches  the  bench  behind. 

The  proper  spacing  of  the  draft  spaces  is  made  by  a  "fot- 
low-board,"  which  is  pulled  up  as  the  bench  rises.  This  is 
merely  an  inch  plank,  with  two  leather  handles,  and  it  is 


76       Clay  Plant  Construction  and  Operation 

supported  by  headers  that  are  occasionally  pushed  thru  as  nec- 
essary. In  rectangular  kilns  one  "follow  board"  will  answer 
the  purpose,  but  in  round  kilns  several  are  required  to  accom- 
modate the  benches  of  different  lengths. 

At  first  sight  this  method  of  setting  appears  to  be  impos- 


FROMT     Cuev*Tion  Seen  on    THRU 

BKMC.M 

Fig.    40.     Tiqht    Bolt    Flat    Setting.      Set   Number   of    Header 
Courses  to  Suit  Quantity  Required. 

sible.  It  gives  the  impression  of  cutting  off  all  draft  and 
of  being  too  tight.  However  this  is  not  the  case.  It  is 
an  old  method  and  perfectly  successful  in  every  respect. 
Less  skill  is  required  in  setting  "tight  bolts"  than  in  any  other 
method.  It  is  extremely  fast,  as  a  setter  can  pick  up  as 
many  brick  as  he  can  clamp  together  between  his  hands 
and  lay  them  in  place  on  the  bench  in  one  movement. 
There  is  absolutely  no  chance  for  "kiln  marking"  and 
the  brick  come  out  of  the  kiln  with  both  faces  of  an 
even  color. 

UNFLASHED    FACE    BRICK   SETTING 

In  spite  of  the  increased  demand  for  flashed  colors 
there  is  still  a  good  demand  in  some  sections  for  brick  of 
a  clear  color,  both  in  dry-pressed,  stiff-mud  and  soft-mud. 
To  prevent  flashing,  it  is  of  course  necessary  to  protect 
the  faces  and  heads.  This  is  accomplished  by  "facing" 
the  brick  and  "butting"  the  heads. 

The  well  known  forms  of  "double  two  on  one,"  "double 
three  on  one,"  and  "double  five  on  two"  are  used,  as 
shown  in  Fig.  35.  With  care  in  burning,  this  type 
of  setting  will  accomplish  the  object  sought  for.  It  re- 
quires, however,  the  greatest  skill,  for  all  brick  must  be 


Setting  Down-Draft  Kilns 


77- 


perfectly  faced  or  many  "seconds"  will  result.  Care  is 
also  necessary,  as  with  all  setting,  that  after  the  first 
course  "is  laid  down  all  brick  shall  be  set  in  perpendicular 
lines,  in  order  that  the  fire  gases  may  flow  unchecked  to 
the  bottom. 

Where  burning  can  be  done  under  continuous  oxidizing 
conditions,  as  'in  cases  where  natural  gas,  producer  gas 
or  oil  are  used,  the  "tight  bolt"  method  can  be  used  with 
success.  With  this  method  only  the  heads  are  exposed  to 
the  gases  under  any  circumstances,  and  if  these  are  not 
flashed,  there  is  the  great  additional  advantage  of  having 
two  faces  to  select  from,  with  no  chance  of  "kiln  marks." 

Protecting  the  heads  exposed  above  the  flash  walls  is  one 
of  the  difficulties  experienced  in  setting  unflashed  face-brick. 
One  of  the  several  methods  used  is  shown  on  Fig.  36. 

FLASHED   FACE   BRICK   SETTING 

Setting  brick  so  as  to  get  flashed  faces  presents  many  diffi- 
culties. In  the  first  place,  if  entire  kilns  of  flashed  faces  are 
required,  the  difficulty  is  often  experienced  of  dealing  with 


Fig.   41.     Combination    Flat   and    Edge   Setting. 

raw  materials  which  will  crack  badly  when  set  flat  to  any 
height.  "Rolling"  or  "tumbling"  often  results  with  this  method. 
The  setting  space  is  reduced  and  there  is  a  greater  tendency 
for  brick  to  stick  at  vitrification  temperatures,  unless  sand  is 
used. 


78       Clay  Plant  Construction  and  Operation 

Fortunately  the  market  for  flashed  brick  has  been  educated 
to  demand  a  wide  variety  of-  flash  marks.  This  allows  the 
manufacturer  to  set  part  of  his  kiln  on  edge  and  part  on 
the  flat.  In  fact,  the  more  varied  the  setting  the  greater  the 
variety  of  marking  and  color. 

Figs.  37,  38  and  39,  show  two  methods  of  setting  entire 
kilns  of  brick  on  their  beds  or  flat  sides.  The  question 
as  to  how  many  brick  can  be  set  on  each  other  before 
the  coursing  is  broken  by  a  "runner"  or  tieing  course, 
and  also  to  what  height  the  setting  can  be  carried,  is 
one  that  must  be  determined  for  each  material.  No  set 
rules  can  be  laid  down  for  this. 

Another  method,  which  was  developed  by  the  author 
and  is  an  adaptation  from  the  "tight  bolt"  method,  is 
shown  on  Fig.  40.  This  has  proved  very  successful, 
and  is  very  stable,  altho  it  gives  only  one  flashed  face.  This, 
of  course,  is  enough  in  a  rough  textured  brick,  but  makes 
it  undesirable  for  smooth  face.  It  will  be  noted  that  the 
flashed  heads  are  taken  care  of  in  the  header  courses.  In  the 
manufacturer  of  rough  textured  brick,  it  is  generally  the  rule 
to  set  combination  kilns,  part  on  edge  and  part  flat.  The 
kiln  is  divided  so  as  to  provide  the  proper  porportion  of  each 
or  only  so  many  are  set  on  the  flat  as  the  material  will 
allow.  Fig.  41  shows  a  kiln  set  in  combination. 


CHAPTER  VIII 


Down-Draft  Kiln  Design 


MUCH  HAS  BEEN  WRITTEN  on  the  subject  of  kilns 
and  much  remains  to  be  written,  but  the  author  is  sure 
that  a  vast  majority  of  clay  workers  will  agree  that  helpful 
information  on  this  subject  has  been  exceedingly  scarce. 
The  reason  for  this  has  been  that  very  little  information 
dealing  with  the  basic  principles  of  kiln  design  has  been 
published. 

To  all  appearances  the  down-draft  kiln  is  a  simple  affair. 
Yet  it  is  with  wonder  and  not  a  little  awe  that  one  goes 
about  this  continent  and  observes  what  a  difficult  and  intri- 
cate proposition  the  average  clayworker  has  made  of  it. 

There  are  good  reasons  for  this  condition  of  affairs.  In 
past  years  too  little  attention  has  been  paid  to  kiln  design 
and  construction.  As  a  general  rule,  when  a  new  kiln  was 
required  or  a  change  was  made  from  the  old  up-draft  to  the 
down-draft  type,  the  matter  was  left  entirely  to  the  superin- 
tendent, burner  or  brickmason.  These  men  often  had  little 
idea  of  even  the  most  simple  principles  underlying  the  burn- 
ing of  clay  wares. 

The  fact  remains  therefore,  that  fully  seventy-five  per  cent 
of  the  kilns  of  this  type  in  use,  and  probably  more,  are  not 
economical. 

A  kiln  may  be  economically  deficient  in  many  ways — it  may 
cost  originally  far  more  than  it  should;  it  may  require  high 
upkeep,  which  means  not  only  repairs,  but  the  loss  while  out 
of  commission ;  it  may  produce  a  high  percentage  of  defective 
ware;  it  may  use  a  far  larger  amount  of  fuel  than  necessary, 
or  require  several  days  longer  to  burn  than  it  should;  it  may 
require  rebuilding  before  it  has  had  a  proper  span  of  life. 
That  a  kiln — a  practically  perfect  kiln — which  eliminates  all 
the  above  faults,  can  be  designed  and  constructed  at  a  reason- 
able cost,  goes  without  saying. 

79 


80       Clay  Plant  Construction  and  Operation 

It  will  be  contended  that  a  kiln  which  will  work  success- 
fully on  one  clay  and  one  class  of  ware  will  not  work  on 
others,  and  that  it  has  been  necessary  to  evolve  special  kilns 
for  all  of  the  different  conditions.  This  may  be  true  in  one 
case  in  one  hundred,  but  not  more. 

The  fact  must  be  apparent  to  all  clayworkers  who  have 
given  the  matter  thought  and  study  that  certain  unbreakable 
rules  govern  the  design  and  construction  of  all  kilns,  and 
that  if  these  rules  are  not  followed,  a  poor  kiln  will  be  the 
result.  What  clayworker  with  a  number  of  differently  de- 
signed kilns  on  his  plant  has  not  noticed  that  certain  of  these 
kilns  give  better  results  than  others?  Has  it  every  struck 
you  that  these  "good"  kilns  may  be  very  nearly  correct  in 
principle,  while  the  "poor"  kilns  are  not? 

TOO    LONG   A    BURNING    PERIOD 

From  experiments  and  investigations  made,  the  author  has 
come  to  the  conclusion  that  the  great  majority  of  clayworkers 
are  taking  too  much  time  in  burning  their  ware.  Most  of 
the  time  is  lost  in  the  watersmoking  and  oxidizing  periods. 
In  many  cases  this  is  not  so  much  due  to  faults  in  kiln  design 
or  construction  as  to  poor  burning  methods.  Often — thru 
fear — a  burner  unnecessarily  prolongs  the  burn  in  the  early 
stages.  In  such  a  case,  of  course,  the  fault  lies  with  the  man 
and  the  line  of  improvement  is  clear. 

The  author  is  quite  certain  that  fully  ninety  per  cent  of 
the  shales  and  clays  on  this  continent  can  be  burned  off  in  six 
days  or  less,  irrespective  of  the  products  produced.  This 
includes  the  entire  burning  period  from  lighting  the  fires  to 
the  finish  of  the  burn.  No  exception  is  made  in  the  cases 
where  ordinary  carbonaceous  shales  are  used,  in  fact  where 
the  carbon  content  of  a  clay  or  shale  is  low,  this  period  should 
be  shortened,  in  the  average  case.  T*he  author  is  quite 
aware  that  such  a  statement  will  draw  forth  a  vast  amount 
of  criticism,  for  many  clayworkers  seem  to  take  pride  in  the 
fact  that  they  take  from  ten  to  twelve  days  to  burn  off  a 
kiln,  and  even  tho  they  were  to  be  absolutely  assured  that 
their  ware  would  finish  in  half  the  time,  would  not  even 
give  it  a  trial. 

As  a  proof  that  the  above  contention  is  correct,  the  author 
would  draw  attention  to  the  fact  that  whenever  continuous 
kilns  have  replaced  down-draft  kilns,  the  burning  period 
(the  period  during  which  the  ware  is  under  heat  treatment) 
has  been  reduced  to  six  days  or  less,  except  in  isolated  cases. 
The  reactions  which  take  place  in  a  continuous  kiln  are  not 
one  bit  different  from  those  in  any  other  type  of  kiln,  and 


Down-Draft  Kiln  Design  81 

it  is  therefore  reasonable  to  suppose  that  what  can  be  done 
in  one  type  of  kiln  can  be  done  in  any  other. 

Primarily,  of  course,  in  order  that  ware  may  be  pushed 
thru  a  kiln  safely  at  a  rapid  rate,  it  is  necessary  that  the 
kiln  be  of  proper  design.  The  conclusions  and  designs  set 
forth  in  this  article  are  not  based  on  theory,  but  actual 
observation  and  practice.  They  were  decided  upon  as  being 
the  most  nearly  correct  after  observing  the  design  and  op- 
eration of  several  thousand  kilns,  located  in  many  sections 
of  the  continent,  and  burning  practically  every  variety  of 
ware,  from  all  sorts  of  raw  material. 

Kilns  after  this  design,  both  round  and  rectangular,  have 
maintained  an  average  burning  time  of  six  days  or  less,  on 
shale  and  fire-clay  brick  and  shale  block — not  on  one  yard, 
but  on  several,  located  at  widely  separated  points.  The  fuel 
consumption  never  exceeds  1,000  pounds  per  1,000  common 
brick  equivalent  and  the  recovery  of  first  quality  ware  aver- 
ages ninety  per  cent  or  over. 

In  the  following  description  the  author  will  attempt  to 
cover  the  important  points  on  both  round  and  rectangular 
kilns.  It  is  not  necessary  to  go  into  the  relative  merits  of 
the  two  types,  for  it  is  largely  a  matter  of  personal  choice, 
but  it  might  be  well  to  say  that  as  regards  cost  the  rectangu- 
lar type  is  slightly  cheaper  to  construct  per  ton  of  holding 
capacity,  particularly  when  built  in  large  units,  while  the 
round  is  considerably  cheaper  in  upkeep  (repairs). 

DRAINAGE 

Thoro  drainage  of  the  bottom  is  one  of  the  most  im- 
portant points  in  kiln  construction.  Much  poor  ware  is  due 
to  damp  bottoms — perhaps  more  than  to  any  other  one  cause, 
altho  this  point  is  often  overlooked.  No  matter  how 
good  the  natural  drainage  may  be,  put  a  network  of  drain- 
tile  under  and  around  each  kiln,  being  sure  the  drains  have 
a  good  fall.  On  yards  where  it  is  impossible  to  get  natural 
drainage  for  kiln  bottoms,  put  in  a  sump  and  keep  it  pumped 
out.  The  best  kiln  on  earth  will  not  give  good  results  if  the 
bottom  is  wet.  Money  spent  for  drainage  will  repay  you 
many  times  over. 

FOUNDATIONS 

The  mistake  is  often  made  of  putting  a  kiln  on  shallow 
foundations.  These  should  always  be  carried,  at  least,  to  a 
point  slightly  below  the  deepest  flue.  Very  few  buildings 
of  any  type  are  subjected  to  the  racking  a  kiln  gets,  yet  you 


82       Clay  Plant  Construction  and  Operation 

would  not  think  of  building  even  a  small  house  without 
carrying  the  footings  at  least  a  few  inches  below  the  base- 
ment floor  level.  The  author  has  examined  many  kilns  with 


the  bottom  of  the  footings  above  the  bottom  of  the  flues  and 
the  result  is  always  a  shaky  and  tumbledown  makeshift.  If 
it  is  necessary  to  build  the  kilns  on  soft  ground,  observe  the 


Down-Draft  Kiln  Design  88 

same  rules  in  designing  the  foundation  as  would  be  followed 
in  putting  a  brick  building  on  the  same  ground.  In  making 
your  calculations,  do  not  forget  to  add  the  weight  of  the  ware 
which  the  kiln  will  hold,  to  the  weight  of  the  structure  it- 
self. 

BOTTOMS 

In  designing  a  kiln  bottom  the  main  points  to  be  considered 
are :  equal  distribution  of  the  gases ;  good  draft,  especially 
in  the  water-smoking  period,  and  ease  of  cleaning.  The  first 
gives  good  ware  over  the  whole  bottom ;  the  second  quick 
burns,  and  the  third  saves  tearing  up  the  floor  and  keeps 
the  kiln  in  commission  the  maximum  amount  of  time. 

Personally,  the  author  is  decidedly  against  the  dead  or 
solid  bottom  type  of  kiln.  Invariably  it  produces  a  higher 
percentage  of  defective  ware  and  takes  longer  to  burn.  The 
problem  of  keeping  the  flues  clean  does  not  enter  into  the 
consideration  because  this  can  be  easily  accomplished  in  a 
well  designed  riddle  or  checkered  bottom. 

In  a  checkered  bottom  kiln  you  get  good  distribution  of 
heat  and,  with  deep  flues,  good  draft  and  easy  cleaning. 

Reference  to  Figs.  42  and  43  will  show  the  method  of  laying 
out  the  bottom  of  a  round  kiln.  By  designing  a  deep,  wide 
auxiliary  flue  running  at  right  angles  to  the  main  or  stack 
flue,  thru  the  centre  of  the  kiln,  all  of  the  secondary  flues 
can  be  given  a  slope  of  approximately  45  degrees.  Thus  the 
latter  will  shed  any  sand,  dirt  or  chips  into  the  large  flues, 
whence  they  are  easily  cleaned  out  thru  the  manhole. 
A  much  simpler  bottom  can  be  built  by  omitting  the  auxiliary 
flue,  and  sloping  all  secondary  flues  to  the  main  flue,  but  in 
this  case  some  of  them  will  not  have  slope  enough  to  shed 
and  it  will  be  necessary  to  rake  them  down  at  times.  So  far 
as  the  burning  results  are  concerned  there  is  very  little  dif- 
ference. 

It  will  be  noted  that  the  large  flues  are  wide  enough  for 
the  passage  of  a  wheelbarrow  and  have  height  enough  for 
a  man  to  work  in.  The  depth  allows  for  a  heavy  accumu- 
lation of  sand  and  dirt  before  it  becomes  necessary  to  clean 
out.  Even  where  sand  is  used  in  setting,  such  a  kiln  will 
run  for  several  burns  without  the  draft  being  affected  by 
choking.  Another  advantage  is  that  such  a  kiln  can  be 
cleaned  out  while  setting  is  going  on,  a  decided  advantage  on 
a  plant  which  is  short  of  kiln  room. 

Reference  to  Figs.  44  and  45  shows  the  method  of  laying 


84       Clay  Plant  Construction  and  Operation 

out  a  rectangular  kiln  bottom.     All  that  has  been  said  with 
reference  to  the  round  kiln  applies  to  this  type. 

The  author  is  well  aware  that,  theoretically,  deep  flues  are 
incorrect,  but  in  this  case  theory  and  practice  do  not  check. 


Fig.    43.     Thirty-Foot    Round    Kiln    Bottom. 

In  actual  practice  he  has  found  the  deep  main  flue  to  give 
a  distinct  advantage  during  the  watersmoking  period,  i.  e., 
good  draft  and  no  water  settle.  In  kilns  of  this  design  there 
has  never  been  the  slightest  sign  of  a  water  settle,  even 
ivhere  the  ware  was  set  continually  in  a  distinctly  wet  con- 
dition. This  is  due  to  the  fact  that  the  dense,  moisture-lad- 
en gases  of  the  watersmoking  period  have  a  better  oppor- 
tunity of  getting  clear  of  the  bottom  courses  than  with 
shallow  small  flues. 

Referring  to  the  construction  of  kiln  bottoms,  the  author 
would  like  to  mention  here  the  very  bad  practice  of  partially 


Down-Draft  Kiln  Design  85 

filling  in  the  kiln  excavation  with  earth,  and  then  building  the 
secondary  flue  walls  or  feathers  on  this  filling.  //  this  is  done 
you  will  have  the  trouble  of  at  least  partially  rebuilding  your 
bottom  within  six  months. 

All  filling  should  be  done  with  hard  burned  brick  or  bats. 
If  nothing  else  is  used  in  the  bottom  and  the  masons  are 
prevented  from  getting  too  generous  with  their  mud,  the 
original  bottom  will  remain  level  for  years.  It  is  very  good 
practice  to  allow  the  paving  course  to  dip  slightly  toward  the 
centre  of  the  kiln.  This  will  allow  the  ware  to  lean  away 
from  the  fires  and  in  a  measure  will  tend  to  overcome  the 
"pull"  on  the  outside  courses. 

STACKS 

Nothing  detracts  from  the  appearance  of  a  yard  more  than 


Fig.    44.     Rectangular    Kiln, 

a  number  of  cracked  and  shaky  looking  kiln  stacks.  Also, 
a  poorly  designed  stack  may  cause  what  otherwise  would  be 
an  efficient  kiln  to  give  poor  results. 


86       Clay  Plant  Construction  and  Operation 

In  round  kiln  construction  a  stack  is  generally  built  to  serve 
two  or  four  kilns.  With  rectangular  kilns,  the  single  or 
double  stack  may  be  used,  but  the  multiple  stack  system  is 
the  cheapest  and  most  popular. 

Single  stacks  should  always  be  built  with  a  separate  inner 
lining.  (Fig.  46.)  This  lining  need  not  be  more  than  four 


inches  thick,  and  is  separated  from  the  outer  casing  by  a 
three-inch  air  space.  Occasional  headers  should  be  shoved 
out  of  the  inner  lining  so  as  to  just  touch  the  outer  shell. 


Down-Draft  Kiln  Design  87 

This  prevents  the  closing  of  the  air  space.  In  a  stack  built 
in  this  way  the  inner  lining  moves  up  and  down  freely  with 
the  expansion  and  contraction  and  prevents  any  cracking  of 
the  outer  shell.  When  two  or  more  kilns  are  attached  to 
the  same  stack,  a  separate  inner  stack  should  be  built  for 
each  kiln,  for  when  two  kiln  flues  enter  the  same  stack  flue, 
the  draft  of  one  is  always  affected  detrimentally  by  the  other. 
If  the  inner  stacks  are  not  built  separately,  as  is  often  the 
case,  but  are  only  divided  by  a  single  wall,  the  temperature 
difference  between  the  two  sides  will  quickly  wreck  the 
entire  inner  stack. 

Instead  of  carrying  the  inner  stack  up  the  total  height, 
it  is  often  carried  only  a  few  feet  above  the  point  where 
the  flues  enter.  This  practice  is  only  completely  successful 
when  the  inner  lining  is  carried  up  at  least  two-thirds  of 
the  total  height  of  the  stack.  This  has  been  determined  by 
experiments  carried  on  by  one  of  the  larger  clay  products 
companies  during  the  past  decade. 

HEIGHT    OF    STACK    FOR    KILN 

It  is  now  generally  conceded  by  well  informed  kiln  de- 
signers that  a  thirty-foot  round  kiln  or  a  single  stack  rect- 
angular kiln  of  equal  capacity  should  have  a  forty-foot 
stack  altho  this  can  be  slightly  modified  if  the  kiln  is  located 
on  high  ground. 

The  question  of  stack  area  is  an  extremely  important  one. 
The  theory  upon  which  ordinary  stacks  are  built  will  not  an- 
swer for  kilns,  and  it  was  therefore  necessary  to  find  just 
.  what  relationship  existed  between  the  grate  area  of  a  kiln 
and  its  stack.  After  a  number  of  years  of  close  observation 
and  experiment  the  author  has  found  that  the  best  results  on 
the  single  stack  type  of  kiln  are  to  be  had  by  providing  one 
square  foot  of  cross  sectional  stack  area  for  each  eleven 
square  feet  of  grate  area.  Thus,  in  a  kiln  with  ninety  square 
feet  of  grate  area,  a  stack  should  be  designed  having  a 
cross  sectional  area  of  approximately  eight  square  feet. 
Other  engineers  reach  approximately  the  same  conclusions 
by  different  methods,  but  the  one  set  forth  seems  to  be  the 
simplest  yet  devised  and  therefore  the  most  useful. 

A  trouble  found  with  most  multiple  stack  kilns  is  that 
they  generally  have  too  many  stacks.  This  is  particularly 
the  case  with  the  earlier  kilns  of  this  type.  In  such  cases  a 
number  of  the  stacks  will  "back  draft,"  i.  e.,  draw  the  wrong 
way  during  various  stages  of  the  burn,  thus  prolonging  it. 


88       Clay  Plant  Construction  and  Operation 

The  author  has  bricked  up  half  the  stacks  in  kilns  of  this 
kind  and  easily  reduced  the  burning  time  by  one  half. 

On  account  of  the  more  equal  distribution  of  the  draft 
and  the  fact  that  less  work  is  required  of  them  individually, 
the  stacks  on  a  multiple  stack  kiln  need  not  be  as  high  as 
for  the  single  stack  type.  However,  the  ratio  of  stack  area 
to  grate  area  is  larger.  In  the  multiple  stack  type  the  proper 
ratio  is  one  square  foot  of  cross  sectional  stack  area  to 
nine  and  tzvo-tenths  (9.2)  square  feet  of  grate  area. 

It  is  good  practice  to  provide  one  T>r  two  stacks  at  each 
end  of  a  multiple  stack  kiln,  no  matter  what  the  length. 
These  stacks  insure  better  draft  at  the  wickets — spots  to 
which  it  is  unusually  hard  to  pull  the  heat  in  any  kiln.  The 
stacks  should  be  equally  spaced,  as  nearly  as  possible,  on 
each  side  of  the  kiln,  and  aside  from  the  end  stacks,  one 
side  stack  should  be  provided  for  each  three  fire-boxes. 

The  proper  draft  will  be  obtained  if  the  stacks  are  carried 
up  to  a  point  six  feet  above  the  inside  top  of  the  crown. 

DAMPERS 

There  seems  to  be  a  great  variance  of  opinion  among  clay- 
workers  as  to  the  best  method  of  dampering  a  kiln,  or  as  to 
whether  a  damper  is  necessary  at  all.  Certainly  the  men  who 
stand  for  the  damperless  kiln  for  all  purposes  cannot  have 
had  a  wide  experience,  for  it  is  obviously  impossible  to  get 
the  required  results  with  all  types  of  clay  when  no  dampers 
are  used.  Instances  of  this  would  be  dark  flashed  face- 
brick  and  salt-glazed  ware.  There  is  not  the  slightest  doubt 
but  that  perfect  results  can  be  gotten  without  the  use  of 
dampers  in  some  cases  and  under  the  direction  of  expert 
burners.  However,  since  about  one  plant  in  fifty  is  equipped 
with  experts,  a  kiln  is  required  which  can  be  handled  by  the 
kind  of  labor  that  is  within  reach  of  the  forty-nine. 

Many  types  of  efficient  dampers  are  available,  but  most  of 
them  present  some  difficulty  in  construction  or  operation. 
The  hinged  damper  at  the  top  of  the  stack  is  very  good,  but  is 
not  at  all  popular,  principally  on  account  of  the  constructional 
difficulties.  The  sheet  damper,  dropped  into  the  stack  flue  or 
shoved  into  the  stack,  is  very  simple  and  very  efficient,  but 
when  made  of  sheet  or  cast  iron  becomes  very  troublesome 
thru  warping.  When  made  of  fire-clay  slabs  or  brick  it  is 
is  cumbersome  and  hard  to  handle. 

Another  type,  but  one  very  seldom  used,  is  very  efficient 
and  is  easy  to  operate,  except  in  cases  where  much  flashing 


Down-Draft  Kiln  Design 


89 


is  done.     This  is  the  wicket  damper.     It  is-  merely  an  open- 
ing  near  the  hasc   of    the   stack   equal    in   area   to   the   cross 


SECT  it  M    XX- A 


Fig.  46.     Two-Stack  Kiln. 

section  of  the  stack.     When  the  kiln  has  full  draft  this  open- 
ing is  closed  with  brick,  mudded  over.    As  it  becomes  neces- 


90       Clay  Plant  Construction  and  Operation 

sary  to  cut  the  draft  the  brick  are  removed  from  the  wicket 
one  at  a  time.  The  rush  of  air  into  the  stack  thru  the 
opening  thus  made,  cuts  the  draft  in  the  kiln  as  effectually 
as  tho  a  sheet  had  been  shoved  into  the  flue.  If  more  draft 
is  required  after  once  cutting,  the  brick  are  put  back  in  the 
wicket.  In  the  single  stack  kiln  it  is  necessary  to  choose 
between  one  of  the  above  methods  and  put  up  with  the  diffi- 
culties encountered. 

Multiple  stack  rectangular  kilns  are  likely  to  require  more 
dampering  than  the  single  stack  round  type,  unless  operated 
by  expert  burners.  This  is  due  to  the  fact  that  if  the  fires 
are  allowed  to  get  hotter  in  one  part  of  a  kiln  than  another, 
the  heat  from  the  balance  of  the  kiln  is  naturally  drawn 
towards  this  "hot  spot."  Some  means  must  be  used  to  cor- 
rect this  condition,  of  course,  and  the  damper  is  usually 
resorted  to,  an  effort  being  made  to  drive  the  heat  to  the 
cooler  portions.  The  author  does  not  wish  to  go  on  rec- 
ord as  saying  that  a  damper  is  necessary  to  correct  such  a 
condition  (as  it  is  not)  but  the  great  majority  of  burners 
are  not  capable  of  handling  the  situation  without  a  damper, 
and  it  therefore  becomes  a  comparative  necessity.  The  design 
of  the  kiln  has  much  to  do  with  the  case.  Proper  stack., 
flue  and  fire-box  proportions  tend  to  make  it  easier  to  control 
and  prevent  such  conditions. 

When  dampers  are  necessary  in  a  multiple  stack  kiln,  the 
easiest  and  cheapest  one  to  use  is  a  flat  sheet  of  iron  laid 
on  top  of  the  stack.  The  stacks  are,  as  a  general  rule,  low 
enough  to  reach  from  the  top  of  the  wall  or  platting.  Any 
of  the  methods  suggested  for  a  single  stack  kiln  may  be  used 
on  the  multiple  stack  type. 

WALLS   AND   CROWNS 

Naturally  there  is  no  standard  thickness  for  kiln  walls, 
but  there  is  a  maximum  limit  to  which  it  is  necessary  to 
build  them.  In  the  absence  of  reliable  data  on  the  subject 
of  furnace  construction  in  our  own  industry,  it  is  necessary 
to  look  to  other  industries  where  the  data  is  more  complete. 
The  metallurgical  and  other  industries  have  done  a  vast 
amount  of  investigating  and  have  recently  paid  special  atten- 
tion to  the  prevention  of  excessive  wall  radiation. 

Three  points  are  generally  kept  in  mind  by  the  clayworker 
when  building  a  kiln;  a  wall  of  sufficient  thickness  to  stand 
the  strain;  a  wall  of  such  thickness  as  to  prevent  excessive 
radiation  and  a  wall  thin  enough  to  conform  to  good  fire-box 


Down-Draft  Kiln  Design  91 

design.  You  can  find  kiln  walls  all  the  way  from  eighteen 
inches  to  six  feet  thick.  The  man  who  built  the  eighteen- 
inch  walls  fulfilled  all  the  requirements  of  strength  and  got 
away  from  one  difficulty — that  of  the  concentration  of  heat 
in  a  deep  fire-box — but  he  got  into  another  difficulty.  He  had 
excessive  wall  radiation.  The  man  who  built  the  six-foot 
walls  got  away  from  excessive  wall  radiation,  but  concen- 
trait-d  the  heat  in  his  fire-boxes,  thereby  entailing  heat  losses 
in  the  walls  and  high  repair  charges  thru  the  frequent 
burning  out  of  his  fire-box  arches. 

In  determining  the  thickness  of  walls  these  difficulties 
must  be  borne  in  mind.  Considered  from  all  angles,  thin, 
straight  walls  are  the  best,  if  they  can  be  insulated,  as  in 
this  case  the  fire-box  is  thrown  inside  the  kiln  and  the  fuel 
does  not  waste  considerable  of  its  energy  in  heating  up  and 
burning  out  the  walls.  The  setting  space  lost  by  projecting 
the  fire-boxes  into  the  chamber,  while  a  considerable  item, 
cannot  be  compared  with  the  saving  of  time,  fuel  and  re- 
pairs during  the  life  of  a  good  kiln.  If  an  uninsulated  wall 
is  built,  it  must  be  as  thick  as  possible  and  still  be  com- 
patible with  good  fire-box  design. 

As  a  general  rule  the  walls  of  rectangular  kilns  are  built 
thicker  than  those  of  round  kilns.  This  is  necessary  on 
account  of  the  difference  in  the  method  of  ironing  the  walls. 
The  bands  on  a  round  kiln  are  much  more  efficient  than  the 
irons  on  a  rectangular  kiln. 

THE    EFFICIENCY    OF    THE    DOWN-DRAFT    KILN 

Before  proceeding  further  with  the  discussion  of  this 
subject  it  would  be  well  to  look  into  the  efficiency  of  the 
down-draft  kiln.  The  author  is  pretty  certain  the  following 
figures  will  surprise  many  clayworkers,  even  tho  this  data 
rius  been  given  wide  publicity.  The  results  represent  heat 
balances  taken  on  three  kilns  working  under  normal  every- 
uay  conditions,  and  probably  represent  average  conditions 
on  the  average  yard,  taken  the  country  over.  The  work  was 
done  under  the  supervision  of  Prof.  A.  V.  Bleininger  of  the 
United  States  Bureau  of  Standards. 

Sewer  Pipe  Kiln— Burned  to  2000°  F. 

Heat  lost  by  flue  gases  (through  stack) 18.60% 

Heat  lost  by  ashes 4.58% 

Heat    lost    by    radiation    and    cooling   ware 71.10% 

Heat   actually   used   in  burning  ware 5.70% 

Paving    Brick    Kiln— Burned   to   2030°    F. 
Heat  lost  by  flue  gases 29.9% 


92       Clay  Plant  Construction  and  Operation 

Heat    lost    by    ashes 3.9% 

Heat  lost  by  radiation  and  cooling  ware 54.9% 

Heat  actually  used  in  burning  brick 11.3% 

Building    Brick    Kiln— Burned    to  2000J    F. 

Heat  lost  by  flue  gases 27.33% 

Heat   lost   by   ashes 3.51% 

Heat  lost  by  radiation  and  cooling  ware 49.61% 

Heat    actually   used   in    burning   brick 19.55% 

Experiments  have  shown  that  approximately  25%  of  the 
heat  stored  in  a  kiln  just  off  fire,  is  recoverable  for  use  in 
waste-heat  drying.  This,  according  to  the  above  table,  leaves 
approximately  25%  a  dead  loss,  due  to  radiation.  Consider 
the  last  and  best  case  in  the  light  of  these  figures.  Roughly 
they  mean  that  on  the  average  yard,  burning  coal  at  $2.00  per 
ton,  and  using  1,200  pounds  (or  $1.20  worth)  per  thousand 
brick,  only  24  cents  in  actual  value  is  being  actually  used  out 
of  each  1,200  pounds.  Actually  96  cents  is  being  lost  out  of 
each  1,200  pounds,  or  $1.60  out  of  each  ton.  A  rather  stag- 
gering loss.  But  the  most  important  point  is  that  out  of  each 
ton  fifty  cents'  worth  is  being  lost  thru  the  wails  and  crown. 

Taking  the  country  over,  it  is  the  author's  opinion  that  a 
good  majority  of  the  kilns  are  losing  well  over  25%  of  their 
efficiency  thru  the  walls  and  crowns,  and  many  of  them 
are  burning  coal  costing  from  $4  to  $6  per  ton. 

Accepting  the  figures  of  25%  loss  and  $2.00  per  ton,  and 
allowing  1,200  pounds  per  thousand  brick,  using  a  thirty-foot 
round  kiln  with  a  holding  capacity  of  65,000  building  brick, 
it  will  readily  be  seen  that  each  time  the  kiln  is  burned  off 
the  amount  of  $19.50  is  being  generously  thrown  to  the 
winds. 

Now  the  question  is — is  this  loss  preventable?  It  is,  to  a 
very  great  extent,  by  the  use  of  modern  engineering  methods  as 
applied  to  furnace  construction  and  heat  insulation.  Almost 
every  industry  but  ours  is  making  a  serious  attempt  to 
prevent  excessive  radiation.  Inquire  what  the  steel  maker, 
the  modern  foundry  man,  the  automobile  manufacturer,  the 
brewer,  baker  and  packer  are  doing  along  these  lines.  Ask 
Henry  Ford  if  insulating  his  numerous  furnaces  did  not  help 
him  cut  his  cost  and  price  last  year.  Even  the  claywork- 
ers,  or  some  of  the  wise  ones  at  least,  insulate  their  steam 
pipes,  boilers  and  sewer  pipe  presses.  Even  the  furnace  and 
heating  flues  or  steam  pipes  in  their  homes  are  often  insu- 
lated. Why  not  the  kilns? 


Down  Draft  Kiln  Design  93 

INSULATING   THE   KILN   WALLS  AND  CROWN 

For  a  number  of  years,  metallurgical  engineers  have  been 
experimenting  on  furnace  walls,  using  various  methods  of 
construction  and  various  materials.  The  dead  air  space  or 
hollow  wall  has  been  thoroly  tried  and  found  wanting.  This 
is  not  due  to  the  dead  air  space  itself,  for  all  successful 
insulating  is  based  upon  it.  The  trouble  is  that  large  air 
spaces  are  not  efficient  at  very  high  or  very  low  tempera- 
tures, such  as  are  found  in  furnaces  or  ice  houses.  The 
air  space  must  be  infinitesimal  in  size  in  order  that  circu- 
lation may  not  be  set  up  when  there  is  a  temperature  differ- 
ence between  two  of  its  walls  or  sides.  Also  it  is  impossi- 
ble to  prevent  leaks  into  large  air  spaces  from  the  outside 
or  inside,  under  the  conditions  existing  in  a  furnace  or  kiln. 
Of  course,  this  utterly  destroys  its  usefulness. 

It  has  been  necessary,  therefore,  to  find  some  material 
which  had  the  properties  of  the  hollow  air  space  and  would 
resist  high  temperatures,  and  at  the  same  time  would  pre- 
vent the  setting  up  of  air  currents.  Several  kinds  of  diato- 
maceous  earth  have  been  most  successfully  used,  the  one 
known  as  "Kieselguhr"  being  perhaps  the  best  known.  Most 
of  this  comes  from  California,  where  very  large  deposits  ex- 
ist. At  the  present  time  it  is  being  manufactured  into  brick 
and  blocks  of  standard  fire-brick  size  and  these  brick  are 
selling  at  a  price  only  slightly  higher  than  a  good  fire-brick. 
It  is  also  used  in  its  raw  state  in  a  furnace  wall  as  is  cork 
or  sawdust  in  a  fireless  cooker  or  ice  house. 

One  inch  of  this  material  has  insulating  qualities  equal  to 
twelve  inches  of  common-brick.  Therefore  one  brick  is 
equal  to  twelve  common-brick  in  thickness  in  a  furnace  wall. 
Numerous  tests  made  in  several  of  the  university  labora- 
tories show  that  a  four-inch  lining  of  insulating  brick  in  a 
furnace  wall  zvhich  is  under  constant  heat,  will  prevent  50% 
to  75%  of  the  radiation.  In  a  kiln  it  should  be  even  greater, 
as  it  is  heated  up  only  periodically.  Taking  the  lowest  per- 
centage of  saving — 50% — and  using  the  figures  the  writer  has 
given  for  the  loss  on  a  kiln  of  brick — the  result  is  a  saving 
of  $0.75  per  kiln.  In  actual  practice  it  would  undoubtedly 
be  greater  than  this,  but  accepting  it,  you  have  a  saving 
of  $234  a  year  on  a  kiln  turning  twice  a  month. 

COST    OF    INSULATION 

Now  what  will  such  a  lining  cost?  In  no  section  of  the 
country  should  a  4^/j-inch  lining  of  this  material  for  a  30- 


94       Clay  Plant  Construction  and  Operation 

foot  round  kiln,  cost  in  excess  of  $100  and  in  some  sections 
not  more  than  half  this  amount.  As  it  will  replace  an  equal 
amount  of  common-brick  and  the  wall  will  be  built  con- 
siderably thinner,  it  can  be  conservatively  figured  that  from 
$30  to  $40  worth  of  common-brick  will  be  replaced.  This 
makes  the  cost  of  the  lining  from  $60  to  $70,  amount  that 
will  be  saved  inside  the  first  year,  figuring  only  the  saving 
on  heat  loss.  To  this  saving  must  be  added  the  increased 
speed  in  burning. 

Fire-brick  is  often  wasted  in  a  kiln.  Where  temperatures  not 
exceeding  2,000°  Fahr.  are  used,  as  is  often  the  case,  it  is  not 
necessary  to  use  nine  inches  of  good  fire-brick.  Four-and- 
one-half  inches  is  quite  sufficient.  Seldom  do  you  find  the 
fire-brick  lining  in  a  kiln  touched,  except  over  the  eyes,  even 
where  very  high  temperatures  are  reached.  In  a  round  kiln 
it  is  not  necessary  to  tie  the  fire-brick  lining  to  the  common- 
brick,  as  in  this  case  the  lining  may  expand  and  contract 
without  reference  to  the  main  wall,  and  it  is  much  easier  to 
repair. 

In  such  a  kiln  the  shape  will  prevent  it  from  pulling  away 
if  the  brick  are  laid  well.  If  the  lining  is  tied  in,  it  should 
be  laid  alternate  headers  and  stretchers,  or  not  to  exceed  two 
stretchers  to  each  header.  Greater  spacing  of  the  headers 
leads  to  their  being  broken  off  by  the  expansion,  leaving  the 
lining  free.  In  a  rectangular  kiln  it  is  always  necessary  to 
tie  the  fire-brick  to  the  backing. 

In  a  round  kiln  which  is  uninsulated,  the  proper  depth 
of  the  fire-boxes  must  be  considered  in  determining  the  thick- 
ness of  the  wall.  For  the  best  fire-box  results  it  should  not 
be  over  forty  inches.  The  walls  of  rectangular  kilns  when  un- 
insulated should  not  exceed  forty-eight  inches  in  thickness. 
When  insulation  is  used,  the  round  kiln  wall  may  be  twenty- 
seven  inches  and  the  rectangular  kiln  walls  thirty-six  inches. 
When  possible,  use  porous  brick  in  the  interior  of  the  wall, 
as  they  are  better  insulators  than  hard  ones.  It  even  pays 
to  make  up  porous  brick  for  this  purpose  by  mixing  a  por- 
tion of  sawdust  or  coal  slack  with  the  shale  or  clay. 


CHAPTER  IX 


Down-Draft  Kiln  Construction 


OO  LITTLE  IMPORTANCE  is  given  to  the  laying  of 
the  common-brick  in  kiln  construction.  The  writer  does 
not  think  it  would  be  far  wrong  to  say  that  more  than  half 
the  kilns  built  are  practically  wrecked  within  the  first  five 
years  thru  poor  workmanship.  Little  or  no  attention  is  paid 
to  the  proper  tying  together  of  the  wall  in  an  endeavor  to 
make  it  act  as  a  unit,  and  also  very  little  attempt  is  made 
to  allow  for  any  expansion.  Poor  mortar  is  very  often  used 
and  it  is  almost  the  rule  to  avoid  the  use  of  cement  mortar. 
Ordinary  lime  mortar,  as  mixed  by  brickyard  labor,  is  totally 
unfit  for  kiln  construction.  A  3  to  1  cement  mortar  with 
10%  lime  putty  added,  is  practically  unequalled  for  this  pur- 
pose. The  wall  should  be  thoroly  bonded  together  and 
every  precaution  should  be  taken  to  prevent  the  masons  from 
filling  up  large  cracks  and  holes  with  mortar.  The  use  of 
chips  and  small  pieces  of  brick  should  also  be  avoided. 

Various  methods,  some  of  which  are  theoretically  good, 
have  been  devised  to  allow  for  the  expansion  of  the  walls  and 
floors.  In  most  cases,  these,  in  actual  practice,  are  very 
poor.  Any  expansion  joint  which  can  become  filled  with 
sand,  mortar  or  chips,  will  only  help  to  wreck  the  kiln. 
Allowing  for  the  expansion  in  the  vertical  joints,  by 
means  of  a  mortar  joint  of  the  proper  thickness  is  un- 
questionably the  best  method.  This  applies  to  both  fire- 
brick and  common-brick,  and  necessitates  the  use  of  the 
trowel  thruout.  In  fact,  the  variation  in  shrinkage  in 
fire-brick  practically  requires  that  the  mud  be  applied  with  a 
trowel.  This  does  not  necessarily  mean  that  the  joint  should 
be  thick,  for  if  it  is  made  thin  and  each  brick  malleted  down 
to  a  level,  a  far  neater  and  more  serviceable  job  can  be  got- 
ten than  by  dipping.  Furthermore,  no  more  time  is  con- 
sumed in  the  laying. 

95 


96       Clay  Plant  Construction  and  Operation 

Ironing  of  kiln  walls  is  a  question  that  is  too  often  given 
too  little  attention  or  ignored.  This  is  probably  due  to  the 
fact  that  up  to  the  time  Prof.  Harrops'  article  was  published 
a  short  time  ago,  practically  no  data  was  available  on  the  sub- 
ject. It  was  simply  a  case  of  judgment  or  observation.  You 
can  find  types  ranging  all  the  way  from  those  tied  up  like  a 
sore  thumb  with  wire  rope,  or  supported  with  log  buck- 
stays,  to  those  sheathed  with  steel  over  the  entire  surface. 

There  is  little  good  judgment  in  spending  from  $2,000  to 
$5,000  on  a  kiln  and  then  for  the  sake  of  saving  $100  or  $200 
cutting  off  from  five  to  seven  years  of  its  life  by  skimping 
on  the  iron  work.  No  matter  how  careful  you  may  be  in 
the  construction  of  your  kiln,  if  you  do  not  sufficiently  band 
or  iron  it,  it  soon  becomes  uneconomical.  Cracks  in  the  walls 
soon  appear,  thru  which  large  volumes  of  cold  air  get  into 
the  kiln,  and  in  a  few  years  it  may  become  so  racked  as  to 
become  practically  worthless. 

STEEL    SHELL    KILNS 

For  round  kilns  the  steel  shell  is  unquestionably  the  most 
efficient.  It  not  only  holds  the  brickwork  absolutely  in  place, 
but  cracks  positively  cannot  open  up.  Add  to  this  the  fact 
that  the  shell  is  a  good  non-conductor  and  you  have  a  list  of 
favorable  arguments  that  insure  a  good  kiln  thruout  its 
entire  life.  There  can  be  no  question  but  that  the  steel  shell 
kiln  will  give — in  fact  has  given — far  longer  life  than  is  pos- 
sible in  any  other  type.  There  is  only  one  argument  against 
it  and  that  is  first  cost. 

Next  to  the  steel  shell  would  come  the  kiln  which  is 
banded  so  as  to  catch  every  course  of  brick.  This  also  is 
expensive,  about  as  much  so  as  the  steel  shell.  It  is  neces- 
sary then,  to  consider  the  minimum  amount  of  ironing  neces- 
sary to  keep  the  kiln  in  good  condition.  Using  Harrops' 
method  of  calculating  the  size  of  a  crown  band  necessary  on 
a  30-foot  round  kiln,  it  is  found  that  one  band  6  in.  x  ^  in. 
is  quite  sufficient.  However,  the  author  has  always  consid- 
ered the  practice  of  using  two  bands  at  the  crown  seat  good. 
Crown  bands,  especially  light  ones,  sometimes  break,  and  if 
two  are  used,  one  may  break  and  still  do  no  damage.  The 
author,  therefore,  figures  on  two  6  in.  x  %  in.  bands  set 
three  inches  apart  at  the  crown  seat.  Below  them,  one  6  in. 
x  l/4  in.  band  is  set  at  the  furnace  arch,  just  catching  the 
top  of  the  arch  brick  or  block.  Central  between  this  band 
and  the  lower  crown  band  is  set  another  of  the  same  size. 
Under  these  bands  and  spaced  9  inches  apart,  vertical  slats 


Down-Draft  Kiln  Construction         97 

4  in.  x  %  in.  should  be  placed,  extending  around  the  kiln. 
These  slats  should  be  caught  firmly  under  the  lower  crown 
band  and  the  bottom  band.  Above  the  crown  bands  two  4  in. 
x  ]/%  in.  bands  should  be  placed,  but  no  slats  are  necessary. 
In  a  round  kiln,  with  furnaces  of  the  proper  proportions,  the 
distance  between  the  furnaces  is  comparatively  so  small  and 
the  opportunity  for  expansion  in  all  directions  so  large  that 
irons  are  unnecessary  to  prevent  deformation.  Care  however, 
must  be  taken  to  have  the  brick  work  particularly  good  at 
these  points  or  poor  results  will  follow. 

IRONING  RECTANGULAR  KILNS 

For  ironing  rectangular  kilns  10  in.  standard  I-beams 
should  be  placed  between  each  fire  box,  also  two  at  each  end. 
At  the  crown  seat  two  sixty  pound  rails  or  one  standard  8  in. 
channel  should  be  set  into  the  wall.  At  each  end  one  rail  or 
smaller  channel  should  be  placed  at  the  same  height.  Below 
these,  and  in  the  same  positions  as  described  for  bands  on  a 
round  kiln,  50  pound  rails  or  6  in.  channels  should  be  used. 
Rails,  when  used,  should  be  set  with  the  bottom  out. 

The  I-beams  should  be  tied  together  with  1%  in.  rods 
across  the  crown.  It  is  very  important  that  these  rods  should 
always  be  kept  tight  enough  to  "sing"  when  tapped  with  a 
hammer.  Many  crowns  are  ruined  by  allowing  these  rods 
to  slacken  and  remain  loose.  They  have  a  bad  habit  of 
constantly  stretching  and  require  careful  watching.  A  rec- 
tangular kiln  crown  is  most  liable  to  injury  when  cooling; 
during  the  firing  period  the  rods  are  stretched  and  when 
the  kiln  cools  down  they  do  not  return  to  their  former  length, 
thus  allowing  the  crown  to  settle  slightly  after  each  burn. 
This  soon  results  in  a  dangerous  or  wrecked  crown. 

THE   KILN   CROWN 

The  subject  of  the  proper  design  and  construction  of  a 
kiln  crown  is  important  also.  If  the  clayworker  can  do  away 
with  the  high  cost  of  crown  and  furnace  repairs,  he  will 
have  very  little  to  worry  about  as  regards  kiln  upkeep. 

Authorities  agree  that  a  down-draft  kiln  should  have  a  life 
of  fifteen  years,  i.e.,  it  should  not  be  necessary  to  rebuild 
the  walls  and  crown  during  that  period.  The  vast  majority 
of  kilns,  without  doubt,  require  at  least  two  crowns  during 
that  time.  There  is  something  wrong  then  with  the  design 
or  construction,  or  both. 

It  is  on  the  smaller  rural  yards  that  are  found  the  most 
glaring  cases  of  poor  crown  design.  These  are  generally 
too  high,  being  built  on  the  "hay  stack"  principal.  On  the 


98       Clay  Plant  Construction  and  Operation 

larger  plants,  the  writer  has  found  the  failures  to  be  not  so 
much  an  account  of  design,  but  principally  due  to  poor  con- 
struction. 

CROWN  SPRING  ACCURATELY  DETERMINED 
The  proper  spring  or  circle  of  a  crown  for  both  round 
and  rectangular  kilns  has  been  very  accurately  determined 
by  experiment,  altho  it  is  quite  apparent  in  looking  around 
that  many  clayworkers  do  not  take  the  trouble  to  find  out 
what  it  is.  For  a  round  kiln  it  has  been  determined  that 
the  distance  from  a  line  drawn  thru  the  points  where  the 
crown  springs  from  the  wall  to  the  top  of  the  inside  of  the 
crown  should  be  one-fourth  (^)  the  diameter  of  the  kiln. 
For  a  rectangular  kiln  this  distance  is  one-third  (V3)  of  the 
inside  width.  These  figures  have  not  only  been  determined 
as  the  best  for  obtaining  a  crown  with  the  longest  life,  but 
also  as  the  best  for  burning  results.  It  is  a  well  known 
fact  that  a  kiln  with  a  high  crown  consumes  more  fuel  per 
unit  of  ware,  takes  longer  to  burn  and  gives  poorer  bottoms 
than  one  with  a  lower  crown.  If  the  crown  is  too  low  the 
top  ware  is  very  likely  to  be  over-burned  or  the  capacity  of 
the  kiln  decreased  in  an  effort  to  avoid  setting  too  close  to  it. 
A  question  considerably  discussed  in  recent  years  has  been 
as  to  the  proper  method  of  starting  the  crown  off  the  walls. 
There  can  be  no  question  but  that  the  skewback  has  dropped 
out  of  use  to  a  very  considerable  extent,  being  replaced  by 
an  arc  of  a  circle  of  very  small  radius  up  to  the  point  where 
the  proper  circle  of  the  crown  is  reached. 

Harrop,  in  discussing  this  subject,  proved  that  theoret- 
ically, the  crown  started  on  skewbacks  exerted  less  total 
thrust  on  the  crown  bands  than  did  crowns  the  other  type,  but 
that  the  thrust  was  exerted  along  a  single  line.  In  the  case  of 
a  crown  started  from  an  arc,  while  the  total  thrust  may  be 
greater,  this  thrust  is  distributed  over  an  area  equal  to  the 
entire  height  of  the  starting  arc,  and  at  any  given  point  is 
comparatively  small.  On  a  round  kiln,  should  the  crown 
bands  break  in  the  case  of  a  skewbacked  crown,  the  entire 
thrust  of  the  crown  is  exerted  along  the  line  of  the  bottom 
)f  the  skew  with  nothing  but  the  friction  of  a  single  mortar 
oint  to  stop  it  from  shearing  off  and  causing  collapse. 
However,  where  the  arc  is  used,  all  of  the  backing,  (which 
in  this  case  is  particularly  heavy  and  should  be  well  tied  to- 
gether), from  the  point  where  the  crown  starts  to  the  top  of 
the  arc,  must  be  pushed  out  before  collapse  can  take  place. 
Moreover,  each  brick  in  the  arc  is  really  a  skewback  and  we 


Down-Draft  Kiln  Construction         99 

therefore   have   the  total   friction   offered   by   a   number   of 
mortar  joints  instead  of  a  single  one. 

So  far  as  actual  practice  is  concerned,  a  number  of  in- 
stances have  been  reported  where  the  arc  has  been  used,  in 
which  crown  bands  broke  under  fire,  and  the  crown  did  not 
suffer  at  all.  On  rectangular  kilns  it  is  harder  to  justify  the 
use  of  the  arc,  but  in  this  case  also,  it  seems  more  reason- 
able to  distribute  the  thrust  over  a  large  area  of  backing  wall 
than  to  concentrate  it  on  one  point. 

SUPPORT   CROWN    ON    MAIN   WALL 

Another  important  point  in  starting  a  crown.  Instead  of 
supporting  the  crown  on  the  fire-brick  inner  lining,  it  should 


15-  O" 


Fig.   47.     Thirty   Foot    Kiln    Sweep. 

be  set  back  on  the  main  wall.  Everyone  has  noticed  that 
crowns  invariably  crack  badly  over  each  fire-box.  This  is 
partially  due  to  the  greater  expansion  over  each  eye  and  par- 
tially to  the  continued  burning  away  of  the  lining  at  this 
point.  Also  it  has  been  noticed  that  when  it  is  necessary 
to  repair  the  fire-brick  lining  over  the  fire-boxes,  a  portion 
of  the  crown  often  conies  down  during  the  tearing  out  pro- 


100     Clay  Plant  Construction  and  Operation 

cess.  If  the  crown  is  set  back  off  of  the  lining  and  is  en- 
tirely independent  of  it,  most  of  the  trouble  will  be  over- 
come. 

In  building  the  crown  of  a  rectangular  kiln,  the  use  of 
forms  and  lagging  makes  the  obtaining  of  the  proper  circle 
easy.  In  round  kiln  construction  several  methods  are  used  to 
obtain  the  correct  circle.  The  accompanying  plate  (Fig.  47) 
shows  a  very  simple  one.  One  of  the  best  features  is  that  if 
a  course  of  brick  slips  from  its  proper  place,  it  must  be  put 
back  before  the  guage  will  revolve.  This  prevents  the  mason 
from  "slipping  something  over"  when  the  superintendent  is 
not  around. 

Designing  a  theoretically  perfect  crown  will  by  no  means 
give  good  results  unless  the  workmanship  is  first-class.  Even 
a  poorly  designed  crown,  if  carefully  built,  will  give  long 
years  of  service.  To  build  a  perfect  crown,  there  should  be 
no  variation  in  the  shrinkage  of  the  fire-brick  and  they  should 
be  dipped  and  malleted  into  place.  In  fact,  where  careful 
work  is  done  in  metallurgical  furnace  construction  a  mini- 
mum variation  in  size  is  demanded,  often  as  low  as  one- 
sixteenth  to  one-eighteenth  of  an  inch.  With  such  brick, 
perfect  work  can  be  done  with  dipped  brick,  but  it  is  almost 
pitiful  to  see  some  clayworkers  attempting  to  use  the  fire- 
brick ordinarily  sold  for  kiln  purposes,  in  this  way.  And 
it  is  even  more  pitiful  to  see  the  crowns  that  result,  not  only 
when  finished,  but  shortly  after,  when  the  brick  begin  to 
fall  out  or  the  crown  begins  to  sag  in  spots. 

By  far  the  best  job  under  average  conditions,  can  be  done 
by  using  the  trowel  and  malleting  the  brick  to  a  level  cours- 
ing, at  the  same  time  using  the  smallest  amount  of  mortar 
possible. 

In  the  case  of  a  round  crown,  each  course  should  be  keyed 
tight  with  a  driven  key.  In  a  rectangular  kiln  the  courses 
should  be  brought  up  to  a  point  where  the  key  will  go  about 
half  way  to  its  seat  with  the  pounding  received  from  a 
wooden  hand  mallet.  It  should  then  be  forced  home  with  a 
sledge  hammer  and  wooden  block.  If  more  attention  is  paid 
by  the  superintendent  or  engineer  to  the  keying  up,  much 
money  and  trouble  will  be  saved  through  the  longlived 
crown  that  will  result.  It  is  a  job  that  should  never  be  left 
to  the  mason's  judgment. 

Vent  holes  are  sources  of  weakness  in  a  crown.  They 
should  not  be  used,  except  at  the  top  or  in  crowns  built  of 
special  block. 


Down-Draft  Kiln  Construction       101 

Rectangular  kilns,  up  to  fifty  feet  in  length,  require  only 
one  expansion  joint  at  each  end  and  none  in  the  middle.  Over 
fifty  and  up  to  one  hundred  feet,  an  additional  joint  should 
be  left  in  the  middle.  Expansion  joints  in  crowns  are  in- 
variably sources  of  weakness.  The  covering  for  an  ex- 
pansion joint  should  always  be  "built  in"  when  possible. 

The  insulation  of  the  crown  is  a  matter  well  worth  con- 
sidering. Why  a  clayworker  will  build  a  four  to  six  foot 
wall  to  prevent  excessive  radiation  and  then  put  a  two  inch 
lagging  on  a  nine  inch  crown  is  a  question  that  has  no 
answer.  Crowns  can  and  should  be  insulated.  If  a  thirteen 
inch  wall  is  carried  up  from  the  base  of  the  crown  to  within 
eighteen  inches  of  the  top  and  the  space  filled  and  tamped 
with  fine,  burnt  out  ashes,  a  very  good  insulation  will  be 
secured.  Over  this  filling  a  lagging  of  brick  should  be  laid 
and  this  covered  with  a  coating  of  lime-cement  mortar. 
Burnt  out  ashes,  especially  the  light  fluffy  kind,  make  an 
excellent  insulation  and  are  generally  procurable  on  a  clay 
plant.  Unburned  carbon  should  always  be  removed. 

FURNACES 

The  writer  is  well  aware  that  this  is  a  subject  the  gods 
themselves  cannot  agree  on,  and  is  not  going  to  attempt  to 
convince  anyone  that  any  particular  type  is  the  best.  There 
are  many  good  ones,  when  used  under  the  proper  conditions. 
The  one  described .  was  selected  after  observing  a  large 
number,  as  being  one  of  the  best  types  for  average  condi- 
tions— fuel,  labor  and  material  considered. 

A  furnace  to  be  adaptable  to  the  average  clay  plant  must 
be,  first — so  designed  that  it  will  properly  combust  ordinary 
or  low  grade  fuels;  second — capable  of  being  efficiently 
handled  by  the  average  laborer;  third — easy  to  control  and  to 
produce  either  reducing  or  oxidizing  conditions;  fourth — 
have  a  low  up-keep.  This  is  a  pretty  large  order  for  any 
fire-box  and  the  writer  does  not  hesitate  to  say  that,  most 
furnaces  fall  down  on  one  or  more  of  these  propositions. 

A  very  important  item  in  kiln  design  is  the  ratio  between 
grate  area  and  kiln  floor  area.  There  are  very  definite 
limits  to  this  ratio  and  if  best  results  are  to  be  obtained 
they  must  be  observed. 

The  upper  limit  is  one  square  foot  of  grate  area  to  four 
square  feet  of  floor  area;  the  lower,  one  square  foot  of  grate 
area  to  eight  square  feet  of  floor  area.  Observation  of  many 
of  the  best  designed  kilns  on  the  continent  lead  the  author  to 


102     Clay  Plant  Construction  and  Operation 


believe  that  a  ratio  of  1  to  7.5  is  the  best  for  average  con- 
ditions. For  the  burning  of  fire-brick  the  ratio  should  ap- 
proach the  upper  limit — 1  to  4 — while  for  handling  a  clay 


with  a  short  vitrification  range,  the  lower  limit  would  be  best. 

For   the   best    results    in   salt-glazing  the    limits    should   be 

confined  between   1  to  6  and  1  to  8.     In  the  great  majority 


Down-Draft  Kiln  Construction       103 

of  cases  1  to  8  ratio  is  the  best.  In  going  below  this  point, 
dull  ware  will  likely  result,  while  to  go  above  1  to  6  gener- 
ally means  blistered,  pimply  ware,  or  at  least  a  considerable 
percentage  of  it. 

The  higher  the  grate  area — floor  area  ratio — the  greater  the 
care  required  in  handling  the  kiln,  especially  near  the  finish 
of  the  burn,  but  increasing  the  grate  area  will  invariably  give 
greater  burning  speed. 

Fig.  48  gives  an  idea  of  the  furnace  suggested.  It  will  be 
noted  that  the  grate  bars  are  easily  gotten  at,  and  that  the  fur- 
nace is  easy  to  clean  and  therefore  likely  to  be  popular  with 
the  firemen.  It  requires  no  doors,  yet  can  be  absolutely  con- 
trolled, as  a  couple  of  shovels  of  slack  will  effectually  close 
the  feed  hole,  or  it  can  be  left  partly  or  entirely  open.  Doors 
are  however,  decidedly  advantageous  on  any  firebox  and  per- 
fect control  and  efficiency  cannot  be  obtained  without  them. 
This  furnace  is  so  simple  as  to  be  very  easy  to  keep  in  repair. 

Especially  should  be  noted  the  distance  from  grate  bars  to 
top  of  arch.  This  is  important  in  any  kiln  furnace.  Plenty 
of  room  is  necessary  over  the  fires  if  the  necessity  of  constant 
repairs  to  the  arch  are  to  be  avoided.  A  low  fire-box  con- 
fines the  heat  and  heats  up  the  kiln  walls  instead  of  the  ware : 
a  high  one  allows  it  to  get  into  the  kiln  where  it  belongs. 

Every  clayworking  plant  wastes  hundreds  of  dollars  each 
year  replacing  furnace  arches  built  of  brick.  If  these  arches 
are  built  of  fire-clay  shapes  or  blocks,  this  trouble  will  be 
eliminated  and  furnaces  will  stand  for  years  without  atten- 
tion. Such  shapes  cost  very  little  more  than  the  equivalent 
in  brick  and  are  carried  in  stock  by  many  of  the  fire-brick 
plants  catering  to  the  clayworker. 

A  word  in  closing  about  bag-walls.  There  are  really  not 
many  types  to  select  from.  It  is  merely  a  question  of  round 
or  square — high  or  low.  The  question  as  to  whether  a  high 
or  low  bag  is  best,  is  one  that  must  be  decided  according  to 
conditions.  It  may  be  necessary  to  build  a  high  bag  to  pro- 
tect the  ware  from  flashing;  to  throw  the  heat  more  to  the 
center  of  the  kiln;  to  prevent  the  ware  from  being  drawn 
into  the  fire-boxes  or  to  prevent  melting. 

So  far  as  shape  is  concerned,  the  author  does  not  think 
there  is  much  question  but  that  the  semi-circular  bag  gives 
the  longest  life.  In  brick  kilns,  where  the  setting  is  run  up 
tight  against  the  bags  the  semi-circular  type  offers  far  greater 
resistance  to  crushing  and  the  pull  of  the  fires  than  the 
rectangular,  and  furthermore  it  is  the  most  economical  so 
far  as  floor  space  is  concerned. 


CHAPTER  X 


Continuous  Kiln  Foundations 


A  LTHO  THE  CONTINUOUS  KILN  has  oral  used  suc- 
^*  cess  fully  for  considerably  more  than  a  halt  century  in 
Europe,  it  is  still  looked  upon  by  the  vast  majority  of  Amer- 
ican clay  plant  owners  as  an  experiment.  Nor  does  this  idea 
disappear  as  rapidly  as  would  be  expected  with  the  ever- 
increasing  knowledge  on  the  subject  As  soon  as  a  clay- 
worker  becomes  a  convert  and  decides  to  build  a  kiln  of  this 
type,  his  neighbors,  or  at  least  many  of  them,  immediately 
begin  to  figure  about  how  long  he  can  remain  in  business 
before  the  receiver  steps  in.  They  are  not  without  justifica- 
tion in  taking  this  attitude,  but  have  very  good  reasons. 

The  continuous  kiln  was  first  brought  to  the  attention  of 
the  American  clayworker  by  Europeans  who  claimed  to  be 
kiln  engineers  and  to  have  some  particular  design  of  kiln 
which  was  their  own  and  which  would  produce  marvelous 
results.  These  men  were  more  often  than  not,  simply  brick 
masons  who  had  helped  to  build  a  kiln  or  two,  or  burners 
who  had  operated  them  for  a  short  period.  The  clay  prod- 
ucts manufacturers  which  these  men  managed  to  interest 
were  the  large  plant  owners  of  that  period.  This  same  type 
of  clayworker  is  still  the  man  most  interested  in  the  con- 
tinuous kiln.  Now,  the  conditions  with  which  these  kiln 
builders  were  confronted  on  this  continent  were  entirely  dif- 
ferent from  those  in  Europe.  Instead  of  kilns  of  ten  thou- 
sand daily  capacity,  those  of  from  twenty  to  fifty  thousand 
capacity  were  required,  and  these  European  brick  masons, 
not  being  engineers,  or  at  the  most  having  a  very  limited 
training,  were  not  equal  to  the  occasion. 

They  did  build  kilns,  but  in  such  a  way  that  the  con- 
tinuous kiln  received  a  "black  eye"  from  which  it  is  still 
convalescing.  Not  only  were  most  of  these  early  kilns  im- 
properly designed,  but  the  construction  was  worse  than  bad 

104 


Continuous  Kiln  Foundations        105 

and  many  of  them  literally  fell  to  pieces  in  a  few  years. 
Very  few  of  those  that  did  stand  up  to  the  work  gave  the 
results  that  were  expected  of  them  and,  for  a  long  time,  it  was 
thought  that,  while  this  type  of  kiln  might  be  successful  on 
small  capacities,  it  would  not  do  for  large  ones. 

Another  condition  that  has  retarded  the  use  of  this  kiln 
on  the  American  continent  is  the  fact  that  most  of  the  in- 
formation— in  the  shape  of  articles — that  has  come  to  the 
clayworker's  attention  has  originated  from  European  sources 
and  has  dealt  with  European  methods  and  results.  These 
articles  make  very  interesting  reading,  but  they  have  little 
effect  in  bringing  the  average  clay  plant  owner  to  the  point 
where  he  is  willing  to  invest  from  forty  to  one  hundred 
thousand  dollars  in  a  kiln. 

As  has  been  said,  the  great  difference  between  American 
and  European  practice  is  the  size  of  the  units  required.  The 
small  European  unit  was  absolutely  useless  on  this  side  and 
it  therefore  became  necessary  for  the  American  engineer  to 
solve  the  problems  of  the  large  unit.  That  he  has  solved  this 
problem  any  man  must  admit  who  will  look  around  with  an 
open  mind. 

This  perfecting  of  the  kiln  design,  however,  was  not  ac- 
complished without  great  expense  and  trouble  to  the  clay- 
workers  who  did  the  pioneering.  The  solving  of  large  prob- 
lems always  costs  money  and,  in  this  instance,  the  clay- 
worker  "paid  the  freight."  This  again  acted  as  a  setback 
to  advancement. 

It  is  the  usual  American  practice  for  the  clay  products 
manufacturer  to  construct  his  own  kilns  whether  they  be 
clamp,  down-draft  or  continuous  kilns.  While  this  prac- 
tice has  developed  some  very  good  designers  and  builders 
of  down-draft  kilns,  it  has  produced  very  few  men  who 
know  anything  about  either  the  design  or  construction  of 
the  continuous  type.  On  the  other  hand,  Europe  has  de- 
veloped many  first-class  continuous  kiln  experts — men  who 
can  design,  construct  and  operate  a  kiln,  and  turn  it  over 
to  the  clay  plant  owner  in  first  class  operating  condition.  Con- 
ditions, however,  are  rapidly  improving  on  this  continent  in 
the  direction  of  design,  and  kilns  are  now  planned  which 
will  give  perfect  results  under  specified  conditions,  providing 
they  are  properly  constructed  and  handled. 

.   CARELESS   BUILDING   SPELLS   DISASTER 

Here  the  important  question  of  construction  comes  to  the 


106     Clay  Plant  Construction  and  Operation 

front.  Having  created  the  condition  under  which  he  is  his 
own  down-draft  kiln  builder,  the  claymaker  must  now  study 
continuous  kiln  construction.  It  is  perfectly  safe  to  say 
that  fully  ninety  per  cent,  of  the  troubles  encountered  in 
the  continuous  kiln  as  it  is  built  today,  are  due  to  con- 


Fig.    49. 


Wrong    Construction    of    Foundation    for 
Batter  Walls. 


structional  faults  and  not  to  faults  in  flue  design  as  was  for- 
merly the  case.  How  to  impress  the  clayworker  with  the  fact 
that  the  "thrown  together,"  cheap,  slipshod  methods  that  have 
been  used  in  down-draft  kiln  construction  will  not  do  in  the 
building  of  a  continuous  kiln,  is  a  problem.  That  he  must  be 
impressed  with  that  fact  in  order  to  save  himself  and  the  in- 
dustry from  further  losses,  is  certain.  A  glance  at  some  of 
the  continuous  kilns  only  recently  built,  to  say  nothing  of 
those  which  are  now  several  years  old,  will  be  enough  to 
convince  anyone  of  their  unstable  construction. 

The  clayworker  has  not  always  been  to  blame  for  this, 
as  in  all  probability,  plans  were  closely  followed.  But  a  little 
thought  and  investigation  would  have  convinced  him  that 
the  designers  had  given  little  consideration  or  cared  little 
about  the  results  the  kiln  would  give  after  a  few  years  of 
service,  or  what  the  repair  bill  would  be.  Some  of  the  poor 


Continuous  Kiln  Foundations       107 

construction  has  been  due  to  the  vicious  practice  of  letting 
the  work  out  on  contract — to  the  lowest  bidder. 

There  is  no  sort  of  construction  known  that  offers  better 
opportunities  for  "skinning"  than  a  continuous  kiln  with  its 
heavy  walls  and  underground  work.  Some  of  the  work  done 
in  this  line  has  been  criminal  and  many  clayworkers  are  to- 
day bemoaning  the  fact  that  they  did  not  know  more  about 
building  when  their  kilns  were  erected. 

The  cost  of  a  continuous  kiln  ranges  from  $25,000  to 
$300,000  and  the  clayworkers  investing  such  amounts  have 
every  reason  to  expect  that  they  will  be  permanent.  If  the 
same  amount  was  to  be  expended  in  a  modern  building  there 
would  be  no  question  whatever  about  the  proper  design, 
construction  and  inspection,  yet  in  the  case  of  a  kiln,  these 
things  are  admittedly  neglected,  and  this  in  spite  of  the  fact 


Fig.    50.      Correct    Construction    of    Foundation    for 
Batter    Walls. 


that  no  other  type  of  structure  is  subjected  to  such  strains 
and  "punishment." 

Continuous  kilns  with  advancing  fire  are  of  two  types — 
gas-fired  and  coal-fired.  Each  type  is  built  in  two  forms — 
chamber  and  tunnel.  All  of  the  continuous  kilns  in  this  coun- 


108     Clay  Plant  Construction  and  Operation 

try  fall  into  one  of  these  classes,  no  matter  by  what  name  they 
may  be  known.  There  is  very  little  difference  in  the  construc- 
tion details  of  the  various  forms,  altho  the  gas-fired  kilns  are 
the  most  complicated.  Some  of  their  features  will  be  treated 
separately. 

GOOD    FOUNDATION    VITALLY    IMPORTANT 

In  designing  and  constructing  the  foundations  of  a  con- 
tinuous kiln  two  important  points  must  be  borne  in  mind, 
first,  the  weight  of  the  structure,  and  second,  its  continual 
movement.  When  calculating  the  load  the  foundation  will 
have  to  carry,  the  figures  must  always  be  based  on  the  kiln 
filled  with  ware.  During  operation,  there  are  some  empty 
chambers  but  often,  when  closing  down,  the  kiln  is  com- 
pletely filled.  It  is  never  safe  to  figure  on  a  load  of  less 
than  one  hundred  pounds  to  the  cubic  foot,  and  it  is  much 
safer  to  figure  one  hundred  and  fifty  pounds.  The  valley 
bottoms,  on  which  kilns  are  generally  located,  are  often  com- 
posed of  sand,  sandy  clay  or  clay  washed  from  the  hillsides. 
Very  often  these  materials  offer  a  very  treacherous  support 
for  a  heavy  structure,  especially  when  every  effort  must  be 
made  to  prevent  unequal  settling. 

If  a  shale  or  rock  bottom  cannot  be  reached  without  in- 
curring great  expense,  an  engineers'  table  should  be  con- 


Fig.   51.      Method    of   Constructing   Weatherproof    Bottom. 

suited  to  find  the  allowable  load  for  the  type  of  material  on 
which  the  kiln  is  to  be  built.  With  this  data  and  the  weight 
of  the  kiln  at  hand,  it  should  be  a  simple  matter  to  figure 
the  area  which  the  foundation  must  cover  in  order  to  prop- 
erly support  the  kiln.  In  cases  where  very  soft  ground  is 
encountered,  it  is  sometimes  necessary  to  build  a  "raft"  of 
concrete  on  which  the  structure  will  "float."  This,  of  course, 
is  very  expensive  but,  in  many  cases,  it  is  the  best  kind  of 


Continuous  Kiln  Foundations       109 

an  investment.  Should  there  be  any  doubt  whatever  in  the 
mind  of  the  plant  owner  as  to  what  load  the  ground  will 
safely  ca«rry,  a  reputable  engineer  should  be  consulted. 

A  clayworker  should  never  accept  the  foundation  plans 
furnished  by  a  kiln  company  or  kiln  builder  without  check- 
ing them  carefully.  Too  often  such  plans  are  "standard" 


y^//^/////A^^f^»^ 


Fig.    52.       Method    of    Constructing    Weatherproof    Bottom. 

and  were  not  drawn  up  with  any  reference  to  the  particular 
job  in  hand.  It  will  pay  handsomely  to  be  cautious. 

A  very  bad  habit  into  which  kiln  designers  have  fallen 
is  that  of  considering  only  the  walls  as  requiring  foundation 
support.  At  times  the  floor  and  the  flues  beneath  are  built  as 
tho  entirely  separate  from  the  walls  and  as  tho  they  were 
not  expected  to  carry  any  load.  This  is  a  great  mistake  in 
any  type  of  kiln,  especially  when  it  is  built  on  soft  ground. 
When  the  floors  and  flues  of  a  continuous  kiln  are  built  in 
this  way,  the  repair  bill  is  likely  to  be  staggering  from  the 
very  beginning.  A  foundation  heavy  enough  to  support  the 
flue  walls,  floor  and  ware  should  always  be  provided  and 
should  be  part  of  the  general  foundation  plan — not  separate. 

A  mistake  very  often  made  in  designing  the  kiln  founda- 
tion is  in  not  providing  "backing"  for  the  foot  of  the  batter 
walls.  By  this  is  meant  that  the  batter  is  started  off  on  a 
smooth,  flat  surface  with  absolutely  nothing  to  prevent  it 
from  shearing  off  at  this  point  whenever  it  gets  the  expansion 
thrust.  This  is  exactly  what  happens  and  there  are  many 
instances  of  these  walls  having  moved  from  six  inches  to 
one  foot  from  their  original  location.  Fig.  50  shows  a  method 
of  providing  a  footing  for  batter  walls  and  Fig.  49  the  usual, 
but  wrong,  method  of  starting  off  the  foundations. 

DRAINAGE    AN    IMPORTANT    POINT 

Proper  drainage  of  the  bottom,  always  an  important  point 
in  any  kind  of  kiln  construction,  is  doubly  important  in  the 
case  of  a  continuous  kiln.  To  be  successful,  a  continuous 


110     Clay  Plant  Construction  and  Operation 

kiln  must  be  capable  of  advancing  rapidly  and,  if  it  does  not 
do  so,  it  is  nearly  always  the  bottom  that  holds  it  back. 
A  vast  majority  of  kilns  of  this  type  are  built  with  solid 


floors,  and  for  this  reason  the  clayworker  figures  that  mois- 
ture under  the  kiln  will  not  bother  him.  This  is  not  the 
case,  however.  When  the  kiln  is  under  fire,  heat  sufficient 
to  evaporate  water  will  penetrate  to  a  depth  of  at  least  ten 
feet.  The  water  vapor  thus  formed  is  constantly  drawn  into 


Continuous  Kiln  Foundations       111 

the  kiln  by  the  slight  vacuum  existing  in  the  chamber  or 
tunnel.  Sometimes  the  amount  of  this  vapor  is  sufficient 
to  make  it  impossible  to  get  from  three  to  six  of  the  bottom 
courses  much  beyond  the  salmon  stage.  It  is  not  only  the 
loss  of  this  ware  that  is  serious,  but  under  such  circumstances 
the  burning  speed  of  the  kiln  is  greatly  reduced  and  conse- 
quently fuel  and  labor  costs  are  higher. 

A  kiln  bottom  should  be  thoroly  drained  to  a  depth  of 
ten  or  twelve  feet  by  running  four-inch  tile  drains  from 
eighteen  to  twenty-four  inches  apart  over  the  whole  bottom 
of  the  kiln.  The  more  fall  these  drains  have,  the  better  they 
will  do  their  work.  They  should  never  have  less  than  one 
per  cent.  All  laterals  should  be  run  into  one  main  drain  of 
sufficient  size  to  take  care  of  the  entire  drainage  system  and 
the  upper  end  of  this  main  drain  should  be  connected  to  the 
main  draft  flues.  This  will  insure  a  slight  circulation  of  air 
in  the  system  and  prevent  any  vapor  from  rising  to  the  kiln 
floor. 

Kilns  are  often  built  in  localities  where  it  is  impossible  to 
get  a  natural  fall  for  a  drainage  system  without  great  ex- 
pense. In  such  cases  all  of  the  drainage  water  should  be 
run  into  a  well  or  sump  and  a  pump  provided  to  keep  the 
water  below  the  proper  level.  The  cost  of  running  the  pump 
will  be  paid  a  hundred  times  over  by  the  increased  capacity 
and  the  higher  quality  of  the  ware. 

Where  it  is  necessary  to  locate  a  kiln  on  gravel  and  in  close 
proximity  to  a  stream  on  approximately  the  same  level,  it  is 
necessary  to  surround  it  completely  with  concrete  walls  and 
bottom,  as  shown  in  Fig.  51.  This  concrete  work  should  be 
thoroly  and  carefully  waterproofed.  Another  method  is  to 
build  the  entire  kiln  on  a  thick  bed  of  concrete  which  extends 
far  enough  out  from  the  walls  to  insure  dryness  in  the  cham- 
bers or  tunnel.  This  method  is  illustrated  in  Fig.  52. 

When  a  kiln  is  to  be  located  so  as  to  have  a  hill- 
side on  one  side  and  a  stream  on  the  other,  provision 
must  be  made  to  take  care  of  the  drainage  water  which 
is  bound  to  flow  from  the  hill  to  the  stream.  Besides 
a  regular  drainage  system  under  the  bottom,  a  concrete  wall 
should  be  erected  between  the  kiln  and  the  hill.  This  should 
be  built  a  little  more  than  the  full  length  (or  width  as  the 
case  demands)  of  the  kiln  and  should  extend  from  the  grade 
line  to  a  depth  of  fifteen  feet.  On  the  side  of  this  wall 
which  faces  the  hill  a  drainage  system  should  be  installed 
that  will  catch  all  water  flowing  towards  the  kiln  and  divert 
it.  Fig.  53  shows  a  plan  and  cross  section  of  such  a  system. 


CHAPTER  XI 


Continuous  Kiln  Walls 


IT  HAS  BECOME  the  general  practice  to  provide  continu- 
ous kilns  with  roofs.  These  roofs  very  naturally  shed  a 
great  deal  of  water  during  wet  weather  and,  in  the  great  ma- 
jority of  cases,  no  troughs  or  down-spouts  are  provided  to 
carry  away  this  water.  To  allow  it  to  soak  into  the  ground 
around  the  kiln  is  exceedingly  bad  practice.  The  damage 
done  in  this  way  in  a  single  year  will  pay  for  properly  trough- 
ing  the  kiln  roof  several  tiroes  over.  When  a  proper  drain- 
age system  is  provided  for  the  kiln  bottom,  the  roof  water 
can  be  led  into  the  main  drain  and  thus  be  carried  away. 

Providing  proper  drainage  is  an  expensive  proposition,  but 
the  clayworker  who  is  not  prepared  to  go  to  such  an  expense 
would  do  well  to  stay  away  from  continuous  kilns  until  he  is 
willing  to  make  the  expenditure.  Nothing  but  regret  has  fol- 
lowed, and  will  follow,  every  attempt  to  "get  by"  without 
paying  the  price. 

SIDE  WALL  CONSTRUCTION    FOR  TUNNEL   KILNS 

Two  types  of  exterior  walls  are  used  in  continuous  kiln 
construction — the  straight,  buckstayed  type  like  those  of  the 
ordinary  rectangular  kiln,  and  the  battered  type,  with  which 
no  buckstays  are  used.  There  is  practically  no  difference  in 
cost,  the  additional  thickness  of  the  batter  wall  being  about 
counterbalanced  by  the  iron  work  of  the  straight  wall.  One 
decided  advantage  the  straight  wall  has  is  the  saving  of  yard 
room.  It  also  has  a  far  better  appearance.  The  batter  wall 
provides  better  insulation  on  account  of  its  thickness,  but 
there  is  no  reason  why  the  straight  wall  cannot  be  provided 
with  four  or  more  inches  of  insulating  brick.  Consideration 
should  be  given  to  the  fact  that  with  the  thick  walls  the 
transfer  men  and  wheelers  must  travel  further.  This  takes 
time  and  is  a  fixed  charge  as  long  as  the  kiln  lasts. 

In  deciding  the  construction  to  be  used  on  the  various 

112 


Continuous  Kiln  Walls  113 

walls,   the   type   of  kiln  and   the  location  of  the  wall   must 
be  carefully  considered. 

It  is  customary  to  build  the  side  walls  of  a  tunnel  kiln 
with  a  one-in-three  batter  on  the  outer  or  exposed  side, 
while  the  inner  sides  are  vertical.  In  the  past  many  kilns 
have  been  built  with  the  outer  and  inner  walls  entirely  sepa- 
rate, the  space  between  being  filled  with  clay,  cinders,  sand 
or  rubbish.  A  large  number  of  such  kilns  have  become  in- 
efficient and  some  of  them  more  or  less  complete  wrecks  on 
account  of  a  lack  of  knowledge  on  the  part  of  the  builder, 
or  poor  workmanship. 

The  fact  that  the  outer  and  inner  walls  expanded  differ- 
ently on  account  of  the  difference  in  temperature  was  also 
entirely  overlooked,  with  the  result  that  the  brace  walls  were 
tied  to  both.  These  were  quickly  torn  to  pieces,  leaving  noth- 
ing but  a  lot  of  loosely  packed  rubbish  to  keep  the  walls  at 
the  proper  distance  and  the  crown  of  the  tunnel  in  place. 
Moreover,  the  loose  filling  worked  its  way  into  the  "inner 
walls  of  the  tunnel  and  quickly  destroyed  them.  Kiln  after 
kiln  has  either  partially  or  entirely  collapsed  on  this  account 
with  consequent  condemnation  of  the  continuous  kiln. 

The  brace  wall  type  of  construction  is  to  be  condemned  if 
for  no  other  reason  than  it  has  been  proven  that  in  the  vast 
majority  of  cases  not  enough  care  will  be  taken  to  make  a 
perfect  job.  Another  and  very  good  reason  is  that  when 
sufficient  care  is  taken  to  make  a  good  job,  the  cost  will  al- 
most equal  that  for  solid  brick  walls.  As  the  principal  idea 
of  the  heavy  wall  is  insulation,  a  thinner  and  stronger  wall 
can  be  built  solid,  with  an  inner  lining  of  insulating  brick  that 
will  not  only  give  better  results  so  far  as  insulation  is  con- 
cerned, but  will  give  better  burns,  longer  life,  and  will  cost 
less. 

As  "filled"  walls  will  continue  to  be  built,  it  is  deemed  wise 
to  describe  the  best  method  of  construction  which  is  shown 
in  Fig.  54. 

The  outside  or  batter  wall  should  be  thirteen  inches  thick, 
with  mortar  joints  at  right  angles  to  the  face.  It  is  not  nec- 
essary to  put  in  header  courses  closer  than  every  fourth 
course.  All  brick  should  be  hard  and  the  mortar  should  be  a 
mixture  .of  three  parts  sharp,  clean  sand  to  one  part  Port- 
land cement.  To  this  may  be  added  ten  per  cent,  of  lime 
putty  to  improve  its  troweling  qualities.  Lime  mortar  should 
not  be  used  under  any  circumstances  because  the  kiln  will  in 
all  probability  be  under  fire  and  subject  to  expansion  strains 


114     Clay  Plant  Construction  and  Operation 

before  the  mortar  could  reach  its  maximum  strength,  or  any- 
where near  it.  The  inner  or  tunnel  walls  proper  should  be 
not  less  than  twenty-seven  inches  thick  and  should  be  laid 
up  with  alternate  header  and  stretcher  courses  thruout.  No 
other  bond  should  be  used  under  any  circumstances,  for  it 
must  be  remembered  that  these  walls  are  continually  "rolling" 
forward  and  backward  thru  expansion  as  the  fire  passes 
around  the  kiln.  The  inner  side  of  the  tunnel  wall  should 
be  lined  with  brick  of  a  refractoriness  suitable  to  the  ma- 
terial to  be  burned.  This  lining  should  never  be  of  common- 
brick. 

FIRE   BRICK   LINING   ECONOMICAL   IN    LONG   RUN 

It  is  hard  to  estimate  the  amount  of  money  that  has  been 
lost  in  the  attempt  to  "save"  a  small  amount  on  the  lining 
by  the  use  of  common-brick.  If  low  temperatures  only  are 
to  be  used,  a  cheap  stiff-mud  fire-brick  will  fill  all  require- 
ments. If  higher  temperatures  are  to  be  attained,  a  better 
grade  of  brick  must  be  put  in.  Seldom  is  it  necessary  or  wise  to 
use  a  high  grade  fire-brick  for  this  work,  unless  the  kiln  is  used 
for  refractories.  Second  or  third  quality  brick  are  sufficiently 
refractory  in  ninety-nine  out  of  one  hundred  cases.  Being 
dense  and  strong,  they  are  much  better  suited  to  this  class  of 
work.  In  cases  where  only  ordinary  heats  are  used,  the 
stretcher  courses  need  only  be  faced  with  four  inches  of  fire- 
brick. Back  of  the  fire-brick,  only  first  class  hard  brick 
should  be  used.  The  use  of  "bats"  and  soft  culls  in  these 
particular  walls  is  a  great  mistake. 

The  brick  (both  refractory  and  common)  on  the  inner 
half  or  thirteen  and  one-half  inches  of  the  walls  should  be 
laid  up  in  fire-clay,  or  fire-clay  and  shale  dust.  The  hori- 
zontal joints  should  be  as  thin  as  it  is  possible  to  make  them 
with  a  trowel  and  mallet.  The  vertical  joints  should  be  about 
one-fourth  inch  wide.  These  joints  are  made  wider  to  allow 
for  the  horizontal  expansion  of  the  kiln.  After  burning, 
each  joint  will  shrink  about  ten  per  cent,  of  its  green  width, 
and  thus  thousands  of  minute  expansion  joints  are  provided 
in  the  length  of  the  kiln.  The  outside  thirteen  and  one-half 
inches  of  this  wall  should  be  laid  up  in  a  mixture  made  of 
fifty  per  cent,  three-to-one  Portland  cement  mortar  and  fifty 
per  cent,  three-to-one  lime  mortar.  This  mixture  has  been 
found  to  give  excellent  results  where  both  Portland  cement 
and  lime  mortars  have  failed.  A  lime  mortar  would  do  the 
work  if  it  really  had  a  chance  to  harden  before  being  sub- 
jected to  heat.  A  clay  mortar  does  not  get  sufficient  heat 


Continuous  Kiln  Walls 


115 


in  the  outside  half  of  the  wall,  to  harden.     It  merely  dries 
out  and  loses  its  bonding  qualities. 

Expansion  joints  one  and  one-half  inches  wide  should  be 


Fig.  54.     Section   of  Wall. 

left  in  the  tunnel  walls  every  twenty  feet.  These  should 
always  be  made  to  come  in  the  center  of  one  of  the  brace 
walls  which  extend  from  the  outside  walls. 

HOW    BRACE    WALLS    SHOULD    BE    BUILT 

Brace  walls  should  be  built  between  the  batter  walls  and 
the  tunnel  walls  on  two-foot  centers.  These  brace  walls 
should  be  thirteen  inches  thick  and  tied  to  the  batter  walls, 


116     Clay  Plant  Construction  and  Operation 

being  bonded  perfectly  with  them  and  the  mortar  joints  c  m- 
tinuing  in  the  same  direction.  These  walls  should  not  be  t  ea 
to  the  tunnel  walls.  If  they  are,  they  will  be  quickly  tc  rn 
to  pieces  by  the  expansion  of  those  walls.  However,  tl.ey 
should  be  built  solidly  against  the  tunnel  walls,  for  it  must 
be  remembered  that  they  take  the  place  of  the  irons  on  a 


Fig.  55.     Door  Construction. 

rectangular  down-draft  kiln.  They  not  only  keep  the  tunnel 
walls  in  place  but  take  the  thrust  of  the  crown.  It  is  for 
this  reason  that  they  must  be  built  close  together,  if  a  long-- 
lived kiln  is  to  result. 

Between  the  batter  and  the  tunnel  walls  the  spaces  are 
filled  with  ground  clay  or  a  mixture  of  ground  clay  and  sand. 
This  filling  should  be  done  as  the  walls  rise,  but  not  before 
the  brickwork  is  sufficiently  strong  to  allow  it  to  be  tombed 
lightly  to  insure  its  being  solid. 

Shale  or  clay  which  has  been  put  thru  a  dry  pan  or  other 
grinder  makes  the  very  best  filler.  It  should  be  just  damp 
enough  to  form  a  ball  when  squeezed  in  the  hand.  The 
great  advantage  of  such  a  filler  is  that  it  will  harden  to  a 
solid  mass  and  will  not  work  into  every  crack  in  the  brick- 
work and  thus  tear  the  kiln  to  pieces. 

Words  cannot  be  found  that  are  strong  enough  to  condemn 
the  common  practice  of  finishing  up  the  walls  and  crowns 
and  then  dumping  into  the  spaces,  the  excavation  from  the 
kiln  bottom,  "bats,"  rubbish  and  anything  else  that  is  handy 
or  in  the  way.  So-called  kiln  builders  are  often  responsible 
for  such  jobs  and  the  clay  worker  only  allows  it  because  of 
ignorance  and  inexperience. 


Continuous  Kiln  Walls 


117 


Door  walls  should  be  thirteen  inches  thick  and  should  be 
well  tied  to  both  batter  and  tunnel  walls.  A  triple  rowlock 
should  be  used  in  the  door  arches,  which  are  shown  in  Fig.  55. 
Too  much  care  cannot  be  used  in  the  construction  of  the 
door  walls  and,  even  under  the  best  of  conditions,  consider- 
able attention  must  be  given  to  them  to  keep  them  in  good 
condition,  especially  where  they  tie  into  the  tunnel  walls. 

SOLID    BRICK    BETTER    THAN    CLAY    FILLING 

A  great  improvement  in  the  above  described  kiln  construc- 


F\g.    56.      Section    of   Solid   Wall. 

tion   is   the   replacing  of   the   clay  filling  between   the  batter 
and  tunnel  walls  with  solid  brick  as  shown  in  Fig.  56  There 


118     Clay  Plant  Construction  and  Operation 

is  very  little  difference  in  cost,  especially  if  No.  2  brick  are 
available,  as  is  often  the  case.  Absolutely  no  difference  should 
be  made  in  the  construction  of  the  batter  and  tunnel  walls,  but 
the  brace  walls  are  left  out  and  what  might  be  termed  a  con- 
tinuous brace  wall  is  built  in  their  stead. 

The  inner  section  of  the  wall  is  a  continuation  of  the  bat- 
ter wall,  the  bond  being  continued,  thru  the  entire  thickness. 


A*IH  «p_  JL  m« 
riA.MXA.ai 


Fig.  57.     Section  Thru   Inside  Wall  Double  Tunnel  Construction. 

It  should  be  built  solidly  against  the  tunnel  wall  but  not  tied 
to  it,  the  latter  being  left  free  to  move  back  and  forth.  Only 
the  outside  thirteen  inches  of  the  batter  wall  need  be  laid 
up  in  cement  mortar,  the  balance  being  laid  in  lime-cement 
or  "spiked"  mortar.  Great  care  must  be  taken  to  have  all 
brick  laid  in  full  mortar  joints.  Laying  the  brick  in  courses 
and  then  slushing  the  mortar  over  the  brick  so  as  to  fill  the 
joints  will  not  do  in  continuous  kiln  construction.  Close,  neat 
bricklaying  should  be  insisted  on  and,  instead  of  filling  up 
wide  joints  or  cavities  with  mortar,  brick  chips  should  be 
used.  The  use  of  "bats"  in  a  thick  wall  is  not  to  be  con- 
demned, providing  it  is  not  overdone.  A  course  of  "bats'' 
laid  with  the  same  care  as  is  given  whole  brick,  and  not  used 
merely  as  a  "filler"  for  a  few  hods  of  mortar,  can  be  used 
quite  frequently  if  they  are  always  tied  top  and  bottom  with 
ivhole  brick.  To  use  course  after  course  of  "bats,"  as  is 
often  done,  produces  only  poor  results. 

Where  the  double  tunnel  construction  is  used  (two  tun- 
nels side  by  side)  the  filling  between  the  tunnel  walls  should 
always  be  of  solid  brick.  Each  tunnel  wall  should  be  built 
separately,  with  the  brick  filling  between  independent  of  them, 


Continuous  Kiln  Walls 


119 


as  shown  in  Fig.  57.    To  tie  these  walls  together  will  wreck 
any  kiln  very  quickly. 

Both  straight  buckstayed  and  battered  walls  are  used  in 
the  construction  of  the  side  walls  of  a  chamber  kiln.  When 
battered  walls  are  specified,  the  construction  should  be  carried 
out  in  exactly  the  same  way  as  described  for  the  tunnel  kiln. 
The.  expansion  joints  should  be  located  at  the  points  where 
the  cross  walls  which  separate  the  chambers  are  set  into  the 
side  walls,  as  shown  in  Fig.  58.  The  same  construction  is  used 
in  straight  wall  kilns. 

THIN    INSULATED    WALL    BEST 

When  straight  walls  are  to  be  used,  several  important  fac- 
tors should  be  borne  in  mind.  Primarily,  the  thin  straight 
wajl  is  built  to  conserve  yard  room.  If,  therefore,  such  a 
wall  is  made  very  heavy,  it  defeats  this  purpose.  On  the 
other  hand,  one  of  the  great  advantages  claimed  for  the  con- 
tinuous kiln  is  low  radiation  losses  due  to  proper  insulation. 
A  thin  brick  wall  is  not  a  good  insulator  and  the  matter, 
therefore,  resolves  itself  into  a  question  as  to  whether  the 
clayworker  will  build  a  thin,  uninsulated  wall  and  put  up  with 
a  constant  radiation  loss;  a  thin  insulated  wall,  which  will 
give  him  yard  room  and  practically  prevent  radiation  losses ; 
or  abandon  the  idea  of  the  straight  wall  and  build  the  bat- 
tered one. 

Considered     from    every    possible    viewpoint — appearance, 


Jo.MTA 


Fig. 


Showing    Location   of   Expansion   Joints. 


space,  working  conditions  and  rapidity  of  construction — the 
thin  insulated  wall  is  the  best  for  the  side  walls  of  the 
chamber  kiln.  It  must  be  remembered  that  this  type  of  wall 
requires  the  utmost  care  in  construction.  Straight  walls 


120     Clay  Plant  Construction  and  Operation 

should  never  be  less  than  thirty-six  inches  thick.  Instead  of 
building  the  inner  wall  separate  from  the  outer,  as  in 
the  tunnel  kiln,  the  entire  wall  is  tied  together  as  in  the 
case  of  a  rectangular  down-draft,  with  alternate  courses  of 
stretchers  and  headers.  See  Fig.  59. 

The  header  courses  should  be  continued  thru  the  entire 
thickness  of  the  wall.  In  the  selection  of  fire-brick  for  the 
inner  lining,  the  same  rules  regarding  thickness  and  quality 
should  apply  as  in  the  case  of  a  tunnel  kiln,  described  above. 
The  inner  thirteen  and  one-half  inches  of  the  wall  should 
be  -laid  up  in  fire-clay  or  fire-clay  and  shale,  the  outside  thir- 
teen and  one-half  inches  in  three-to-one  Portland  cement 
mortar  with  ten  per  cent,  lime  putty  added,  while  the  inner 
nine  inches  may  be  laid  in  50-50  lime-cement  mortar.  The 
fire-clay  should  be  laid  exactly  as  described  for  the  tunnel 
kiln. 

Insulating  brick  should  be  used  as  the  insulator.  Four  and 
one-half  inches  of  this  material  would  be  sufficient,  but  in 
order  to  get  a  perfect  bond,  it  is  necessary  to  use  four  and 
one-half  inches  on  the  stretcher  courses  and  nine  inches  on 
the  header  courses.  They  should  be  laid  up  as  shown  in  Fig. 
59,  as  they  are  not  as  strong  as  building  brick  and  this  con- 
struction is  stronger  than  a  straight  bond. 

URGE    USE    OF    INSULATION    BRICK 

The  use  of  insulating  brick  in  kiln  construction  is  still 
novel  to  American  clay  workers.  There  is  some  reason  (altho 
very  little)  why  a  man  who  is  building  a  down-draft  kiln 
costing  from  $2,000  to  $4,000  should  decide  against  their  use. 
He  may  expect  to  be  out  of  business  in  a  few  years — and 
possibly  will  be,  if  the  balance  of  his  plant  is  wasting  as  much 
money  for  him  as  his  uninsulated  kilns — or  he  may  simply 
regard  the  down-drafts  as  a  "hold  over"  until  he  can  afford 
to  build  a  continuous  kiln.  However,  for  the  man  who  makes 
up  his  mind  to  spend  from  $25,000  to  $300,000  on  a  continu- 
ous kiln,  there  is  not  the  slightest  excuse  for  overlooking 
this  elementary  principal  of  heat  engine  construction.  A 
moment's  consideration  of  the  fact  that  four  inches  of  this 
material  is  equal  to  from  thirty-two  to  forty-eight  inches  and 
nine  inches  equal  to  from  seventy-huo  to  one  hundred  and 
eight  inches  of  common-brick  work,  insofar  as  insulating 
qualities  are  concerned,  should  be  enough  to  convince  any 
man  of  intelligence  that  its  use  is  absolutely  necessary.  It 
would  be  by  all  means  advisable  for  the  man  who  will  not 


Continuous  Kiln  Walls 


121 


consider  the  use  of  this  material,  to  abandon  all  thought  of 
a  straight  wall  and  use  the  battered  wall  instead  for,  in  the 
latter  case,  the  design  in  itself  will  give  him  the  insula- 
tion which  is  absolutely  necessary  for  perfect  results. 

It  must  be  admitted  that  the  insulating  brick,  which  are 
at  present  on  the  American  market,  have  very  little  strength 
and,  for  this  reason,  some  clayworkers,  who  have  investigated 
them  have  been  afraid  to  use  them.  It  is  not  at  all  necessary 
for  a  clay  plant  owner  to  go  into  the  market  when  requiring 
a  brick  of  this  kind.  Almost  anyone  can  make  a  good  in- 
sulating brick  on  his  own  plant.  The  principal  ingredient 
of  the  standard  insulating  brick  is  a  diatomaceous  earth 


CMANH 


Fig.  59.    Section  of  Straight  Wall  Kiln.     Also  Section  Showing  Iron 

Work. 


known  as  "Kieselguhr."  This  material  can  be  obtained  in 
the  raw  state  and  any  particular  quantity  of  it  mixed  with  anv 
plastic  clay  and  burned.  Naturally  the  greater  the  quantity  of 
kieselguhr  used,  the  weaker  will  be  the  brick,  as  it  is  a  non- 
plastic  substance,  but  the  greater  will  be  its  insulating  value. 
However,  almost  any  good  plastic  clay  or  shale  will  carry  fifty 
per  cent,  or  more  of  this  material  and  still  be  as  strong  as 
many  brick  considered  strong  enough,  for  kiln  work.  An- 
other and  cheaper  method  of  making  a  fairly  good  insulat- 
ing brick  is  to  make  a  mixture  of  fifty  per  cent  sawdust  and 
fifty  per  cent  clay  or  shale  and  burn  it  to  a  fair  hardness. 
The  burning  out  of  the  sawdust  leaves  a  porous  body  that 


122     Clay  Plant  Construction  and  Operation 

makes  a  good  insulating  brick  of  fair  strength.  Of  course, 
each  brick  would  not  have  the  'insulating  value  of  standard 
insulating  brick,  but  where  they  are  used,  the  thickness  of 
the  insulating  wall  could  be  increased  in  proportion. 

Ten-inch  "I"  beams  should  be  used  as  buckstays  in  the 
construction  of  a  straight  wall  chamber  kiln.  These  should 
be  space  ten  feet  on  centers  for  satisfactory  results.  The 
beams  should  be  tied  together  at  the  top  with  one-and-one- 
half-inch  rods  having  a  turnbuckle  in  the  center.  The  beams 
should  be  set  in  heavy  concrete  footings  to  a  depth  of  at 
least  three  feet.  Tying  the  beams  to  the  bottom  of  the 
kiln  walls  by  means  of  a  ring  bolt  and  a  plate  buried 
in  the  masonry,  and  eliminating  the  footings,  as  has  been 
done  on  some  American  kilns,  is  utterly  useless.  It  is  sim- 
ply fastening  them  to  the  wall  they  are  supposed  to  hold 
in  place. 

Six-inch  channels  should  be  built  into  the  face  of  the 
wall,  flat  side  out,  at  the  height  of  the  door  arch  skewbacks, 


Fig.  60.     Section  of  End  Batter  Wall  Showing  Cross-Over  Flue. 

and  extending  from  door  opening  to  door  opening.  One 
channel  of  the  same  size  should  be  run  the  full  length  of 
the  kiln  just  above  the  door  arch,  and  another  half  way 
between  it  and  the  top  of  the  kiln.  See  Fig.  59. 

END   WALLS  OF   TUNNEL    AND   CHAMBER    KILNS 

American  practice  is   fast  getting  away   from  the  original 
method  of  building  circular  or  oval  kilns  with  the  chambers 


Continuous  Kiln  Walls  123 

or  tunnel  running  completely  around  the  structure,  on  ac- 
count of  the  inaccessibility  of  the  end  chambers.  The  setting 
of  'such  kilns  often  offers  no  particular  difficulty,  but  when 
the  ware  is  to  be  loaded  on  cars,  it  means  costly  wheeling. 
The  newer  types  are  the  double  battery,  single  battery,  or 
double  tunnel  single  battery.  In  these  kilns  the  "cross  over" 
is  made  thru  flues  from  one  tunnel  to  another  or  one  battery 
to  another. 

In  the  circular  type  there  is  often  considerable  trouble  thru 
the  end  chambers  or  tunnels  being  comoelled  to  take  the  ex 
pansion  thrust  of  the  entire  kiln.  When  kilns  are  constructed 
in  this  manner  the  outside  end  walls  must  be  built  consid- 
erably thicker  than  the  side  batter  walls,  with  special  attention 
being  given  to  that  part  of  the  wall  which  is  to  take  the  thrust 
of  the  floor  and  the  crown.  The  batter  should  be  the  same  as 
for  the  side  walls,  and  the  space  between  the  lining  and  the 
outside  wall  should  always  be  of  solid  brick,  with  the  mortar 
joints  continuing  those  of  the  batter  wall  right  thru  to  the 
lining.  In  other  words,  a  solid  batter  wall  should  be  built 
from  outside  to  lining.  The  lining  should  be  built  as  in  the 
side  walls  and  of  the  same  thickness,  for  in  this  part  of  the 
kiln  also,  the  lining  must  be  free  to  expand  separately. 

BUILD     BATTERED     END    WALLS 

In  the  case  of  the  newer  types,  the  end  walls  are  always 
battered  and  are  built  straight  across  the  end.  This  con- 
struction gives  far  greater  stability  than  the  circular  end,  and 
is  much  easier  to  hold  in  place.  It  must  always  be  borne 
in  mind  that  these  end  walls  take  an  enormous  thrust.  Even 
small  kilns  are  150  feet  long  and  some  of  the  larger  ones 
several  hundred  feet  in  length.  The  expansion  of  such  a 
mass  of  brickwork  will  quickly  wreck  any  but  the  best  con- 
struction. In  the  case  of  the  chamber  kiln,  where  the  cham- 
bers and  crowns  run  at  right  angles  to  the  side  walls,  the 
whole  thrust  of  from  eight  to  twenty  crowns  must  be  taken 
entirely  on  the  ends,  and  any  accident  to  these  walls  would 
mean  the  collapse  of  the  crowns,  like  a  house  of  cards.  Ex- 
amination of  several  kilns  in  which  occasional  brace  walls 
and  earth  filling  were  used  between  the  end  batter  walls  and 
the  lining,  instead  of  solid  brick,  has  shown  that  the  thrust 
of  a  kiln  is  great  enough  to  crush  the  mortar  joints  from  be- 
tween the  brick,  and  in  some  cases,  even  the  brick  themselves 
were  crushed  to  fragments.  In  each  case,  this  happened  in 
less  than  five  years  after  the  kilns  were  built. 

The  "cross-over"  flues  or  those  used  to  carry  the  heat  from 


124     Clay  Plant  Construction  and  Operation 

one  tunnel  to  another,  or  one  battery  of  chambers  to  another, 
are  sometimes  built  within  the  end  walls.  Whenever  a  flue 
is  to  be  built  within  these  walls,  it  should  be  built  so  that 
the  top  of  the  arch  comes  entirely  below  the  floor  level.  It 
will  be  seen  that  to  build  such  flues  where  they  will  have 
to  take  some  of  the  expansion  thrust,  is  to  invite  disaster;  in 
fact,  practice  has  shown  this  to  be  the  case.  Fig.  60  shows 
the  proper  construction. 


CHAPTER  XII 


Partition  and  Flue  Walls 


'"pHE  PARTITION  WALLS,  or  the  walls  which  divide  the 
•••  chambers,  present  no  difficulties  in  the  coal-fired  kiln. 
They  need  not  be  very  heavy,  22^  inches  being  sufficient. 
Their  principal  duty,  aside  from  separating  the  chambers,  is 
to  support  the  crowns.  As  they  are  simply  middle  walls  with 
a  crown  springing  from  each  side,  the  thrust  is  equally  bal- 
anced and  need  not  be  considered. 

In  the  case  of  the  one  side  gas-fired  chamber  kiln  the  con- 
ditions are  different,  however.  In  these  walls  are  built  the  gas 
"down-takes"  leading  from  the  distributing  flues,  which  flues 
are  built  between  and  parallel  with  the  crowns.  These  "down- 
takes"  are  usually  nine  inches  square  and  open  at  the  bottom 
into  the  bag  walls.  Extreme  care  is  necessary  in  the  con- 
struction of  these  walls,  or  gas-leaks  into  the  chambers, 
thru  the  brickwork,  will  cause  serious  annoyance  and  par- 
tial loss  of  control  of  the  gas  at  the  burners. 

The  only  safe  method  of  constructing  these  small  flues 
in  the  walls  is  by  the  use  of  tongue  and  groove  brick 
which  are  shown  in  Fig.  61.  These  brick,  which  are  made 
by  all  the  large  refractory  manufacturers,  are  provided  with 
a  tongue  and  groove  much  like  ordinary  flooring,  and  with 
them  a  perfectly  gas-tight  joint  can  be  made.  They  have 
been  used  by  the  by-product  coke  oven  builders  for  all 
gas  conveying  flues  for  years  past,  with  excellent  results. 
As  yet,  gas-fired  kiln  builders  have  not  used  them  with  the 
result  that  gas-leaks  from  built-in  flues  have  been  a  serious 
drawback  to  kilns  of  this  type. 

As  the  partition  walls  are  built  up,  the  "down-take"'  flues 
should  be  carried  up  separately,  as  the  tongue  and  groove 
brick  will  not  bond  with  the  standard  shapes.  This  is  really 
an  advantage,  as  a  crack,  that  might  develop  in  the  flue  wall, 
would  not  then  extend  thru  the  partition  wall  proper.  The 
flue  walls  need  only  be  four  and  one-half  inches  thick  and,  as 

125 


126     Clay  Plant  Construction  and.  Operation 

tongue  and  groove  brick  are  made  very  exact  in  size  on  ac- 
count of  the  nature  of  their  use,  they  should  be  dipped  in  the 
mortar.  The  partition  walls  should  be  laid  up  with  a  trowel 
.and  mallet  and  the  bond  should  be  the  same  as  the  lining, 
alternate  courses  of  stretchers  and  headers.  They  should  be 
set  into  the  side  walls  as  shown  in  Fig.  58.  When  nine  inch 
by  nine  inch  "down-take"  flues  are  used  the  total  wall  thick- 
ness should  be  thirty-six  inches. 

In  the  gas-fired  and  in  some  coal-fired  chamber  kilns,  bag 
walls  or  pockets  are  built  on  one  or  both  sides  of  each  cham- 
ber and  attached  to  the  partition  walls.  These  bag  walls, 


Fig.      61.        Tongue      and      Groove     Shapes. 

being  built  comparatively  close  to  the  partition  walls,  are 
much  more  stable,  and  are  'not  subjected  to  the  same  destruc- 
tive influences  as  in  the  case  of  bags  in  the  periodic  kiln. 
These  walls  are  often  built  the  full  length  of  the  chamber  with 
only  a  tie  at  the  top  and  middle  on  each  side  of  each  burner 
or  pocket.  This  is  very  poor  practice.  In  such  cases  the 
fame  is  readily  pulled  to  hot  spots  in  the  chamber,  being 
carried  along  behind  the  continuous  bag  wall  before  it 
reaches  the  top.  Thus  the  operator  has  difficulty  in  regulat- 
ing the  kiln.  The  bag  wall  may  be  built  as  a  continuous 
wall,  but  it  should  be  thoroly  tied  irito  the  partition  wall 
from  top  to  bottom  by  means  of  four  and  one-half  inch 
partitions  placed  between  each  burner  or  pocket  as  in  Fig. 
.62.  In  some  cases  each  burner  or  pocket  is  provided  with 
an  individual  bag  wall  completely  surrounding  it.  The 
face  of  a  long  bag  wall  should  be  nine  inches  thick  and 


Partitions  and  Flue  Walls 


127 


should  be  alternate  header  and  stretcher  courses.  Bag 
walls  in  these  kilns,  when  properly  built,  will  last  for  years 
with  only  minor  repairs. 

FLUE    CONSTRUCTION 

The  construction  of  flues  in  and  around  a  continuous  kiln 
is  a  problem  of  considerable  magnitude  insofar  as  making  them 
trouble-proof  is  concerned.  Many  of  the  flues  are  very  diffi- 
cult to  get  at  and  repairing  them  is  not  an  easy  matter.  In 
constructing  a  kiln,  even  from  plans  of  good  kiln  engineers, 
this  question  of  get-at-able-ness  should  be  thoroly  considered. 
It  must  be  remembered  that  the  kiln  engineer  is  generally 
thru  with  his  part  when  the  kiln  is  complete.  He  is  seldom, 
if  ever,  called  upon  to  undertake  the  repairs  which  may  be 
necessary  a  few  years  later. 
Very  often  a  practical  clay- 
worker  with  his  experience  with 
other  types  of  kilns,  can  im- 
prove vastly  on  the  ideas  of 
the  engineer  when  it  comes  to 
a  question  of  flue  location.  The 
design  of  various  flues  is  also 
important  Many  kiln  builders 
have  only  one  idea  in  mind  in 
designing  a  flue,  no  matter 
where  it  is  located,  and  that  is 
that  the  half  circle  arch  is  the 
strongest  that  can  be  built. 
This  idea  is  perfectly  logical 
when  the  flue  has  to  carry  a 
heavy  load,  or  is  located  under- 
ground where  it  will  be  sub- 
jected to  the  bumping  of  carts 
or  wagons.  In  cases  where 
flues  do  not  carry  loads  but 
are  subjected  to  a  thrust  which 
tends  to  crush  their  sides  in, 
the  half  circle  arch  is  unques- 
tionably weaker  than  one  that 
is  flatter.  Experiments  have 
shown  that,  for  flues  subject- 
ed to  a  thrust,  the  rise  of  the  arch  should  be  one-third  the 
inside  width.  Such  an  arch  acts  as  a  brace  for  the  walls  and 
will  keep  them  in  place. 

Continuous  kiln  experts  generally  advise  placing  flues  as  low 
in  the  body  of  the  kiln  as  possible.     This  has  a  tendency  to 


Fig.     62.       Bag     Wall. 


128     Clay  Plant  Construction  and  Operation 

make  them  less  accessible,  but  at  the  same  time  less  likely 
iu  be  damaged  by  constant  expansion  and  contraction.  In 
me  coal-fired  kilns  the  only  flues  used  are  the  main  draft 
flue  with  its  connections,  and  the  watersmoking  flues  when 
piovided.  These  flues  offer  no  constructional  difficulties  and 
may  safely  be  made  part  of  the  brickwork  which  surrounds 
them.  Extra  care  should  be  taken  when  connecting  one  flue 
to  another  so  that  no  break  will  occur.  Care  should  also  be 
taken,  as  in  the  case  of  all  flues,  to  use  the  exact  arch,  wedge 
and  rectangular  shapes  required  to  make  a  perfect  arch.  The 
use  of  straights  alone  will  invariably  lead  to  trouble  and  re- 
pairs. Provision  should  be  made  for  getting  into  the  main 
and  watersmoking  flues  at  various  points  for  examination 
and  repairs.  It  is  no  easy  matter  to  have  to  tear  out  part 
of  a  wall  or  crown,  or  to  remove  several  feet  of  filling,  per- 
haps at  a  point  where  no  trouble  exists,  to  make  a  minor 
repair.  Manholes,  giving  access  to  these  flues,  can  be  left 
so  as  to  make  it  an  easy  matter  to  get  into  them. 

A  very   different  problem  confronts  the  builder  of  a  gas- 


AftCM    liue. 


Fig.   63.     Section   Thru   Gas  Distribut- 
ing   Flue    and    Down    Take. 

fired  kiln.  In  kilns  of  the  latest  design,  all  of  the  gas  and 
watersmoking-  flues  are  carried  in  the  walls.  In  the  older 
models  of  the  chamber  type,  the  main  gas  flue  and  water- 
smoking  flues  were  carried  on  top  of  the  kiln.  These  flues 


Partitions  and  Flue  Walls  129 

were  of  steel  with  a  fire-brick  lining.  This  prevented  loss 
of  heat  and  gas-leaks,  and  as  they  could  expand  and  con- 
tract freely  without  reference  to  the  kiln,  they  gave  ab- 
solutely no  trouble. 

BRICK    GAS    FLUES    HARD    TO    BUILD 

Carrying  gas  in  brick  flues  which  are  subjected  to  consid- 
erable  racking  is   a  ticklish  proposition,   the  construction   of 


CL/SY 


Fig.    64.      Method    of    Lining    Gas    Flue. 

such  flues  requiring  the  best  kind  of  engineering  and  work- 
manship. The  conditions  in  a  kiln  are  entirely  different  from 
those  in  a  by-product  coke  oven  where  brick  gas  flues  are  used 
very  successfully.  In  the  latter  case  the  temperature  sur- 
rounding the  flues  is  practically  constant  and  consequently  the 
walls  are  not  cracked,  but  in  a  kiln  the  temperature  fluctuates 
with  the  location  of  the  fire. 

The  walls  of  the  main  gas  flue,  which  always  runs  the  full 
length  of  the  kiln,  should  be  built  of  tongue  and  groove  brick, 
should  be  nine  inches  thick,  and  have  alternate  header  and 
stretcher  courses.  The  floor  of  the  flue  should  not  be  tied  to 
the  wall  on  which  it  rests  but  should  be  free.  The  arch 
should  be  built  with  extreme  care  and  with  the  joints  as  thin 
as  possible.  The  walls  of  the  flue  must  not  be  tied  to  the 
brickwork  on  each  side.  This  brickwork  should  be  run  up  on 
each  side  of  the  flue  with  a  straight,  close  joint,  without  mor- 
tar between  it  and  the  flue.  If  the  flue  is  to  be  entirely  sur- 
rounded by  brickwork,  that  is,  placed  low  down  in  the  body 
of  the  kiln,  another  arch  should  be  thrown  over  the  flue  arch, 
but  entirely  separate  from  it.  Such  a  flue  will  be  entirely  free 


130     Clay  Plant  Construction  and  Operation 

to  move  without  reference  to  the  adjacent  brickwork,  and  it 
must  be  free  if  it  is  not  to  be  a  constant  source  of  trouble  and 
expense. 

HOW   TO   CONSTRUCT   WATERSMOKI NG    FLUES 

The  watersmoking  flues,  when  built  in  the  body  of  the  kiln, 
must  be  constructed  in  exactly  the  same  way.  As  a  general 
rule,  no  great  pains  are  taken  with  these  flues  because  they 
carry  only  hot  air,  but  when  poorly  constructed,  are  often 
more  of  a  nuisance  than  a  help  on  account  of  the  air  leaks. 
Some  watersmoking  flues  have  been  so  poorly  built,  in  both 
gas  and  coal-fired  kilns,  that  their  use  has  been  entirely 
abandoned. 

The  distributing  flues  in  a  gas-fired  chamber  kiln  are  very 
often  the  source  of  a  great  deal  of  trouble.  They  are  at 
right  angles  to  the  length  of  the  kiln,  so  are  not  subjected 
to  the  same  racking  as  the  main  gas  flues,  but  receive  a  move- 
ment due  to  the  hot  gases  within  them  and  to  the  rise  and 
fall  of  the  crowns  on  each  side.  These  flues  are  supported 
on  the  partition  walls  and  must  be  made  part  of  them,  as 
from  twelve  to  eighteen  "down-take"  'flues  are  led  from  the 
bottom  of  each  flue,  thru  the  partition  walls,  to  the  burners. 
Usually  the  earth  filling  which  covers  the  crowns,  completely 
surrounds  the  sides  and  arch  of  each  flue,  so  that  they  are 
free  to  move.  When  not  carefully  constructed  they  can  cause 
much  trouble  and  annoyance  thru  the  gas  leaking  into  the 
chambers  and  causing  a  loss  of  gas  control. 

TONGUE  AND  GROOVE  BRICK  MAKE  TIGHT  WALLS 

These  flues  should  be  built  of  tongue  and  groove  brick 
and  should  be  nine  inches  thick.  Brick  should  be  dipped  and 
malleted.  The  arches  are  particularly  important.  The  gas 
control  valves  seat  in  the  bottom  .of  these  flues  and  the  valve 
stems  extend  up  thru  the  arches  by  means  of  small  holes.  It 
is  quite  common  for  these  stems  to  ''freeze"  in  the  holes  thru 
an  accumulation  of  tar  around  them.  In  such  cases,  it  often 
takes  all  of  a  man's  strength  to  pull  them  loose  and,  in  do- 
ing this,  the  arch  key  is  loosened,  as  the  pull  is  directly  with 
the  key.  In  course  of  time  the  arch  is  loosened  to  such  an 
extent  that  it  must  be  rebuilt.  This  difficulty  is  entirely  over- 
come by  the  use  of  large  key  blocks  instead  of  ordinary  arch 
or  key  brick.  These  blocks  should  be  large  enough  and  heavy 
enough  to  resist  any  ordinary  pull  against  them.  They  are 
shown  in  Fig.  63. 

When  lining  metal  flues,  it  is  far  cheaper  to  have  special 


Partitions  and  Flue  Walls 


131 


circle  blocks  made  that  fit  the  steel  shell  exactly  than  to  use 
brick.  To  line  up  a  steel  tube  from  one  hundred  and  twenty- 
five  to  two  hundred  feet  long  with  nine  inch  shapes  is  an 
enormous  job  and,  when  finished,  is  more  often  than  not 
something  of  which  to  be  ashamed.  A  mason  cannot  do  good 


work  with  small  units  while  sitting  down  or  lying  on  his 
stomach,  especially  by  lantern  light.  When  quarter  circle 
blocks  of  the  correct  circumference  are  used,  they  can  readily 
be  slipped  into  .place  without  mortar  and  a  good  permanent 
job  results.  See  Fig.  64. 


132     Clay  Plant  Construction  and  Operation 

ROLLERS    PERMIT    EXPANSION    OF    METAL    FLUES 

The  expansion  of  metallic  flues  is  taken  care  of  by  means 
of  rollers  which  allow  the  flue  to  work  back  and  forth  freely. 
Special  care  should  be  taken  at  the  points  where  these  flues 
make  a  right  angle  turn.  At  such  points  two  sets  of  rollers 
with  a  plate  between  should  be  provided  in  order  that  the 
flue  may  move  in  both  directions.  These  rollers  are  laid  at 
right  angles  to  each  other  as  shown  in  Fig.  65.  Four  two- 
inch  steel  balls  laid  between  two  plates  will  answer  the  same 
purpose,  as  in  Fig.  66. 

Where  a  metallic  flue  enters  a  brick  flue,  provision  must  be 
made  to  take  care  of  the  expansion  of  the  former.  If  the 
metallic  flue  is  tied  into  the  brick  flue  it  will  quickly  destroy 
the  connection  and  often  cause  considerable  damage  to  the 
surrounding  brickwork.  When  the  brick  flue  continues  in  the 
same  direction  as  the  metallic  flue  the  latter  should  extend 
into  the  brick  flue  and  be  allowed  to  slide  back  and  forth  in  it. 


Fig.    66.      Method    of   Taking    Care    of    Expansion    in   Two 
Directions  at  Flue  Elbows. 

The  joint  is  then  mudded  over  when  necessary.  When  a 
horizontal  metallic  flue  is  connected  to  a  vertical  brick  flue, 
the  bottom  of  the  metallic  elbow  should  be  built  with  a  wide 
flange.  This  flange  should  simply  rest  on  the  walls  of  the 
brick  flue  so  that  it  may  slide  back  and  forth  freely.  In  this 
case  also  the  joint  is  simply  mudded  tight  when  necessary  or 
closed  with  a  sand  seal  as  shown  in  Fig.  67. 

BUILD    UP-TAKES    SEPARATE    FROM    KILN    WALLS 

When  vertical  brick  flues  or  "up-takes"  are  built  to  convey 


Partitions  and  Flue  Walls 


133 


gas  from  underground  flues  to  flues  in  the  upper  part  or  on 
the  top  of  the  kiln,  they  should  be  made  entirely  separate  from 
the  kiln  walls.  Such  flues  are  often  heated  to  fairly  high 
temperatures,  especially  during  a  "burn  out,"  and  they  must 
be  allowed  to  expand  freely.  They  should  be  built  eighteen 
inches  thick  with  alternate  courses  of  headers  and  stretchers. 


Fig.  67.     Elbow  on   Brick  Flue. 


The  corners  should  be  fitted  with  three-inch  angles  for  the 
entire  height  and  these  angles  should  be  tied  together  every 
three  feet  with  seven-eighths  of  an  inch  iron  rods.  The  in- 
terior four  and  one-half  inches  should  be  of  second  quality 
fire-brick  laid  up  in  a  mixture  of  fire-clay  and  shale,  the 
balance  of  the  wall  being  laid  up  in  a  three  to  one  Port- 
land cement  mortar.  The  fire-brick  in  the  lining  should  be 
hard  and  the  joints  thin.  Producer  gas  has  a  tendency  to 
"rot"  soft  brick  and  fire-clay  mortar,  and  will  destroy  a 
flue  in  a  few  years,  if  the  proper  precautions  are  not  taken. 
Underground  flues,  with  the  exception  of  gas  flues,  serve 
the  same  purpose  in  both  coal  and  gas-fired  kilns.  They 
are  generally  confined  to  main  draft  flues  and  "cross-over" 
or  "return"  flues.  The  latter  are  used  to  carry  heat  from 
one  tunnel  to  another  or  from  one  end  of  a  battery  to 
the  opposite  end.  These  flues,  being  generally  subjected 
to  yard  traffic,  must  be  built  with  a  high  arch,  preferably  a 
half  circle.  Two  points  must  be  particularly  borne  in  mind 
in  constructing  these  flues — they  should  be  as  tight  (free 


134     Clay  Plant  Construction  and  Operation 

from    leaks)    as    it    is    possible    to    make    brick    construction, 
and   they   must   be   very  strong  to   carry  the  loads. 

The  draft  flues  are  not  subjected  to  high  temperatures  and, 
therefore,  may  be  built  of  common-brick.  The  "crossover" 
or  "return"  flues  are  seldom  subjected  to  more  than  1,400 
degrees  Fahr.,  so  that  as  a  rule  common-brick  with  a  high 
melting  point  will  serve  for  them.  The  best  wall  for  all  un- 
derground flues  is  one  thirteen  inches  thick,  with  a  header 
and  stretcher  on  each  course,  the  header  being  reversed  on 
every  course  so  that  it  is  outside  on  one  and  inside  on  the 
next  above  as  in  Fig.  68.  This  bond  breaks  the  vertical  joints 
in  such  a  way  that  none  of  them  go  thru  the  wall.  The 
draft  flues  should  be  laid  up  in  three  to  one  Portland  cement 
mortar  entirely,  while  the  heat  flues  should  have  the  inside 
four  inches  laid  in  clay  or  shale  mortar  and  the  outside  nine 
inches  in  Portland  cement.  All  joints  should  be  as  thin  as  it 
is  possible  to  make  them. 

EXPANSION    JOINTS    NECESSARY    IN    CROSSOVERS 

When  it  is  necessary  to  build  "return"  or  "crossover"  flues 
over  fifty  feet  long,  as  in  the  case  in  the  single  battery  kiln, 
or  when  two  batteries  are  widely  separated,  expansion  joints 
in  the  flues  should  be  left  every  forty  to  fifty  feet.  If  this 
is  not  done,  the  flues  will  wreck  themselves  in  a  few  months, 
to  say  nothing  of  the  effect  on  transfer  tracks  and  pavements 
above  them.  This  also  applies  to  long  underground  gas  flues 
which  expand  greatly  when  being  "burned  out." 

When  digging  a  trench  for  an  underground  flue  it  must 
only  be  wide  enough  for  the  flue  to  fit  snugly.  To  follow  the 
usual  custom  and  dig  a  wide  trench  and  afterwards  fill  along 
the  walls  with  loose  earth  invariably  results  in  a  wrecked 
flue,  for  as  soon  as  weight  is  put  upon  the  arch  the  walls 
spread  and  the  key  of  the  arch  is  gone.  More  continuous  kiln 
trouble  results  from  air  leaks  in  flues  and  walls  than  from  all 
other  sources  combined,  and  many  unsuccessful  or  partially 
successful  kilns  would  work  perfectly  if  the  leaks  could  be 
stopped.  An  instance  of  this  is  a  kiln  which  required  two 
fans  operating  to  capacity  to  get  the  required  draft.  The 
flues  and  walls,  which  were  poorly  constructed,  were  gone 
over  thoroly.  Repairs  were  made  and  leaks  daubed  up,  with 
the  result  that  one  fan  running  three  quarters  speed  gave 
sufficient  draft  and  increased  capacity. 

Underground  gas  flues  should  be  built  in  the  same  manner 
as  other  underground  flues  but  should  have  a  double  arch,  the 


Partitions  and  Flue  Walls 


135 


upper  ring  being  laid  in  cement  mortar.  On  top  of  this  arch 
a  covering  of  sand  several  inches  thick  should  be  laid  as  a 
seal  for  the  gas. 

All  underground  flues  should  be  completed  before  the  main 
body  of  the  kiln  is  put  up.  A  number  of  serious  collapses 
have  taken  place  thru  making  excavations  for  underground 
flues  in  close  proximity  to  the  kiln  walls  after  the  kiln  was 
well  along.  The  weight  of  the  kiln  simply  pushed  the  foot- 
ings out  as  soon  as  the  solid  earth  backing  was  removed  in 
digging  the  trench.  As  some  of  the  flue  excavations  are  quite 
large  and  as  the  flues  may  as  well  be  put  in  first  as  last,  it 
pays  to  take  no  chances  in  this  direction. 

REGARDING   THE   CROWN    OF   THE    KILN 

The  crowns  are  comparatively  the  most  expensive  part  of 
the  ordinary  continuous  kiln  and  it  pays  well  to  so  construct 
them  that  they  will  be  permanent.  It  has  been  the  custom  to 
build  all  these  crowns  as  a  half  circle,  on  the  supposition  that 
such  a  crown  had  the  greatest  strength.  This  idea  would 
have  been  correct  if  the  load  on  the  crown  was  the  only  con- 
sideration. However,  it  is  the  fire  under  the  crown  and  the 
expansion  that  must  receive  first  consideration  and,  on  this 
account,  the  idea  of  the  half  circle  crown  has  had  to  be  re- 
vised. Another  consideration  is  the  kiln  capacity.  In  both 
the  tunnel  and  chamber  types  where  the  half  circle  croxvn 
is  used,  the  skewback  has  to  be  set  so 
near  the  floor  line  that  the  benches. of 
ware  commence  battering  after  the  first 
few  courses.  This  not  only  cuts  capaci- 
ty, but  makes  the  setting  more  expen- 
sive. 


Fig.     68.       Flue 
Wall     Construction. 


Experiments  have  shown  that  the  same 
rules  apply  in  continuous  kiln  crown 
construction  as  in  rectangular  down- 
draft  construction.  This  means  that  the 
best  crown  has  a  height  equal  to  one 
third  the  width  of  the  tunnel  or  cham- 
ber. Such  a  crown  not  only  gives  good 
capacity,  but  the  best  burning  results. 


The  crowns  should  be  built  in  the  most  careful  man- 
ner. The  mortar,  which,  of  course,  should  be  fire-clay, 
should  be  laid  on  as  thinly  as  possible  with  a  trowel  and  each 
brick  malleted  down  to  the  course  level.  With  the  brick 


136     Clay  Plant  Construction  and  Operation 

ordinarily  supplied  for  kiln  work,  it  is  impossible  to  lay  up 
a  permanent  crown  with  dipped  brick.  The  brick  work,  both 
straights  and  shapes,  are  of  such  uneven  thickness  that  the 
difference  cannot  be  made  up  without  the  use  of  a  trowel,  no 
matter  how  skilled  the  mason  is.  If  a  clay  worker  insists 
on  dipping  his  brick  he  must  specify  the  allowable  variation 
in  size  that  he  will  accept  when  buying  the  brick.  In  this 
way  he  may  get  what  he  wants,  but  in  no  other. 

The  proper  number  of  wedges  and  straights  should  be  used 
to  make  the  arch  come  up  perfectly.  The  key  should  fit  so 
tight  that  it  will  not  go  more  than  half  way  to  its  seat  when 
pounded  with  a  hand  mallet.  It  should  then  be  driven  home 
with  a  wooden  block  and  sledge  hammer.  In  the  tunnel  kiln 
the  crown  is  not  subjected  to  the  severe  flame  flash  that  a 
periodic  kiln  crown  gets  above  the  flash  walls.  The  heat  is 
quite  evenly  distributed  and  the  crown  is  heated  up  and 
cooled  off  under  the  best  possible  conditions.  For  these  rea- 
sons a  tunnel  kiln  crown,  if  well  built  and  supported  on  good, 
well  backed  up  walls,  will  have  an  exceedingly  long  life. 

On  top  of  the  nine-inch  crown  proper  a  4J^-inch  arch 
should  be  built.  This  may  be  of  common-brick  laid  in  clay 
or  shale  mortar.  If  the  work  on  this  false  crown  is  well 
done,  it  will  add  considerable  to  the  strength  and  life  of  the 
fire-brick  crown.  The  spandrels  should  be  brought  up  solid 
to  the  top  of  the  crown. 

EXPANSION    JOINTS    IN    CROWN 

Expansion  joints  two  inches  wide  should  be  left  in  the 
crown  every  twenty  feet  at  the  same  points  at  which  the  ex- 
pansion jcints  in  the  lining  occur.  These  joints  should  ex- 
tend thru  the  nine-inch  crown  only.  The  4J/£-inch  false  crown 
should  cover  the  joints  in  the  nine-inch  crown  but  should 
have  one-inch  expansion  joints  left  in  it  at  other  points  twenty 
feet  apart.  On  top  of  this  joint  a  rowlock  of  brick  should  be 
laid  as  in  Fig.  69.  If  the  expansion  joints  extend  thru  the 
entire  crown  and  are  merely  covered  with  a  rowlock,  trouble 
is  almost  certain  to  occur  within  a  year  or  two. 
The  constant  movement  of  the  crown  shifts  the  loose  brick 
covering  the  joints  and  finally  one  or  more  drop  into  them 
and  wedare  them  apart,  resulting  in  the  shifting  of  the  entire 
crown.  Moveover,  as  the  brick  covering  shifts,  the  earth  fill- 
ing  begins  to  work  its  way  into  the  joints  with  the  same  result. 
At  the  points  where  the  false  crown  covers  the  expansion 
joints,  fire-brick  should  be  used  instead  of  common-brick  if 
the  temperatures  to  be  attained  warrant  it. 


Partitions  and  Flue  Walls  137 

While  a  tunnel  kiln  crown  built  of  nine-inch  straights  and 
shapes,  with  a  covering  arch  of  common-brick,  will  give 
perfect  satisfaction  when  properly  constructed,  a  much  better 
but  slightly  more  expensive  crown  can  be  built  of  I%y2-inch 
arch  blocks  made  to  order  for  the  required  radius.  These 
blocks  cost  only  a  little  more  than  their  nine-inch  equivalent 
in  standard  brick,  and  should  be  as  large  as  can  be  con- 
veniently handled  by  the  masons.  The  blocks  should  be 
marked  by  the  manufacturer  and  laid  up  according  to  blue- 
print. Unquestionably,  crowns  built  in  such  a  manner  repre- 
sent the  highest  type  of  construction  and,  it  is  only 
because  most  clay  plant  owners  prefer  the  path  of  least  re- 
sistance and  will  not  go  to  the  trouble  of  ordering  special 
shapes,  that  more  such  crowns  are  not  built  on  either  con- 
tinuous or  periodic  kilns. 

DROP  ARCHES  A  SOURCE  OF  TROUBLE 

Drop  arches  are  usually  a  source  of  constant  trouble  in  a 
tunnel  kiln  on  account  of  the  everlasting  necessity  of  repairs. 
This  is  generally  due  to  the  use  of  standard  brick.  The  best 
practice  calls  for  an  arch  eighteen  inches  deep  and  it  is  a 
pretty  hard  matter  to  build  these  arches,  and  make  them  "stay 
put,"  with  nine-inch  straights  and  shapes.  Splendid  results 
have  been  obtained  by  the  use  of  large  eighteen-inch  fire- 
clay blocks.  These  blocks  must  be  made  to  order  and  the 
units  should  be  as  large  as  possible  for  convenient  handling. 
If  the  blocks  are  hard  burned,  of  perfect  fit,  and  are  laid  up 
with  a  dipped  joint,  drop  arch  troubles  will  disappear. 

When  coal-fired  chamber  kiln  crowns  are  built  of  nine-inch 
brick,  the  same  construction  rules  should  be  followed  as  have 
been  laid  down  for  tunnel  crowns,  but  in  this  case  there  is  far 
more  reason  for  the  use  of  the  large  blocks.  In  the  tunnel 
kiln  the  arch  is  built  in  the  direction  of  the  greatest  expan- 
sion and  is  not  exposed  to  any  great  thrust  from  the  sides, 
but  in  the  chamber  kiln  the  chambers  are  built  at  right  angles 
to  the  length  of  the  kiln  and  are  subjected  to  linear  expan- 
sion and  to  the  thrust  of  the  chambers  on  each  side.  This 
thrust  has  a  tendency  to  "roll"  them  in  the  direction  of  the 
advance  of  the  fire.  Most  of  the  crown  deformation  has 
been  due  to  the  half  circle  design,  for  it  will  be  obvious  to 
anyone  that  the  higher  the  arch,  the  greater  will  be  the  ease 
with  which  it  can  be  crushed  out  of  shape.  The  fact  that  any 
movement  which  takes  place  in  the  crown  must  be  in  the 
mortar  joints,  is  another  reason  for  the  use  of  large  blocks 
as  these  eliminate  a  very  large  percentage  of  the  joints. 


138     Clay  Plant  Construction  and  Operation 

In  the  coal-fired  kilns  the  feed  holes  should  be  constructed 
of  heavy,  hard  burned  blocks  made  to  fit  perfectly  in  the 
crown.  These  feed  holes  are  subjected  to  considerable  wear 
and  the  use  of  standard  brick  will  prove  a  source  of  continual 
renair  exoense. 

GAS-FIRED    KILNS    HARD    ON    CROWNS 

In  the  case  of  the  gas-fired  kiln,  entirely  different  conditions 
are  encountered.  Whether  they  be  fired  on  one  side  or  both, 
the  crowns  are  subjected  to  a  constant  flame  bath  during  the 
firing  period,  the  effect  of  which  is  severe.  Experiments 
have  been  carried  on  long  enough  to  determine  the  fact  that 
the  nine-inch  crown  will  not  stand  up  for  any  length  of  time 
under  the  conditions  to  which  it  is  subjected.  In  this  case 
there  is  no  alternative,  the  33^-mc/t  special  block  crown  must 
be  built. 

In  the  gas-fired  kiln  which  has  fires  on  only  one  side  of 
the  chamber,  the  cost  of  crown  repairs  has  been  staggering. 
All  of  these  crowns  have  been  built  of  nine-inch  straights 
and  shapes,  and  have  had  a  half  circle  arch.  The  kilns  have 
scarcely  been  put  into  service  before  the  crowns  began  to 
flatten  over  the  bag  wall  and  inside  of  a  few  years,  it  has 
been  the  general  rule  that  crown  replacements  and  repairs  be- 
gan. Replacing  a  continuous  kiln  crown  is  not  the  compara- 
tively simple  matter  of  replacing  a  periodic  kiln  crown.  In 
the  former  case  it  is  necessary  to  remove  and  replace  tons 
of  filling,  and  often  to  rebuild  flues  which  are  disturbed,  to 
say  nothing  of  the  necessity  of  bracing  up  the  crowns  on 
several  chambers  on  each  side  of  the  one  being  repaired,  to 
prevent  collapse.  The  cost,  therefore,  amounts  to  about  twice 
as  much  as  would  be  the  case  in  a  periodic  kiln  crown  of  the 
same  size. 

There  is  not  the  slightest  question  but  that  a  long-lived 
crown  can  be  built  on  a  kiln  of  the  one-side-fire  type,  but  it 
must  be  borne  in  mind  that,  being  subjected  to  very  severe 
and  unusual  conditions,  every  precaution  in  regard  to  design, 
material  and  workmanship  must  be  taken.  Any  attempt  to 
cheapen  or  slight  the  work  will  multiply  the  original  cost 
many  times  over  after  a  few  years  of  operation. 

In  setting  the  forms  for  a  crown  it  must  be  remembered 
that  it  will  settle  about  one  inch  after  the  forms  are  removed. 
Due  allowance  must  therefore  be  made  for  this  settle. 

BRACING   OF  CROWNS    BETWEEN    CHAMBERS 

Bracing  between  the  crowns  of  a  chamber  kiln  is  an  im- 
portant detail.  In  the  coal-fired  and  double-gas-fired  types  it 


Partitions  and  Flue  Walls 


139 


is  very  easy  to  brick  up  solidly  between  each  crown  and  this 
should  be  done.  When  this  is  done  it  is  almost  a  guarantee 
against  any  deformation. 

In  the  case  of  the  one-side  gas-fired  kiln  the  gas  distribut- 
ing flues  interfere  with  solid  bracing.  In  this  case  the  dis- 
tributing flues  should  be  placed  as  high  as  possible  and  solid 
brace  walls  from  one  crown  to  another  be  built  up  to  the  bot- 
tom of  the  distributing  flues.  Any  attempt  to  brace  against 
these  distributing  flues  will  result  in  their  being  crushed,  and 
this  must  be  avoided. 

Filling  over  the  tops  of  the  crowns  should  not  be  done  un- 


i"  E 


Fig. 


Section    of    Crown    Showing    Expansion    Joints. 


til  the  entire  battery  or  kiln  is  completed.  The  easiest  method 
of  doing  this  is  to  hoist  a  dump  car  to  the  top  and  run 
tracks  the  full  length  of  the  kiln.  The  material  can  then 
be  spread  evenly  over  the  entire  top.  Many  kilns  have  been 
badly  damaged  during  the  operation  of  filling  thru  commenc- 
ing at  one  end  and  filling  to  the  required  depth  before  moving 
on.  This  throws  an  immense  weight  on  one  portion  of  the 
structure  and  creates  a  strain  that,  in  extreme  cases,  may 
cause  collapse. 

This   is  especially  true  of   chamber  kilns.     To   concentrate 
a   load   on   any   one   chamber   at   a   time   when    much   of   the 


140     Clay  Plant  Construction  and  Operation 

masonry  is  in  a  green  state  will  invariably  cause  the  crowns 
to  "roll"  and,  in  some  cases,  the  movement  has  been  so 
marked  that  portions  of  the  kiln  have  had  to  be  rebuilt. 

As  the  filling  is  carried  to  the  top  it  should  be  evenly  dis- 
tributed over  the  whole  top  from  one  end  to  the  other.  Prim- 
arily, this  filling  is  intended  as  an  insulator  and  naturally  the 
thicker  it  is,  the  greater  its  insulating  value.  As  a  rule  this 
filling  should  not  be  less  than  two  feet  thick  over  the  highest 
point  of  the  crown.  It  may  be  heavier  if  the  plant  owner  is 
willing  to  stand  the  expense.  The  walls  of  the  kiln  must,  of 
course,  be  brought  up  to  the  level  of  the  top  of  the  filling. 

A  covering  of  six  inches  of  burnt  out  ashes  next  to  the 
crown  makes  an  excellent  insulator,  when  they  are  avail- 
able. For  the  balance  of  the  filling,  almost  any  sort  of 
earth  may  be  used.  The  platting  on  top  of  this  filling 
should  not  be  laid  for  six  months  or  a  year  after  the  kiln 
commences  operation  if  a  good  level  floor  is  desired.  The 
filling  is  bound  to  settle  and  shrink  for  a  long  time  and 
nothing  will  prevent  a  poor,  unsatisfactory  job  if  the  plat- 
ting is  put  down  at  the  time  the  kiln  is  built. 


CHAPTER  XIII 

Kiln  Roof  and  Producer  House 
Construction 


'VTO  ATTEMPT  will  be  made  to  describe  chimney  con- 
struction.  Very  few  American  clay  workers  will  con- 
sider the  use  of  a  chimney  in  connection  with  a  continuous 
kiln,  and  the  few  who  still  believe  that  a  chimney  is  cheaper 
than  a  fan,  would  do  well  to  study  the  problem  from  all 
angles  before  making  a  decision. 

It  will  be  admitted,  of  course,  that  a  fan  is  cheaper  to  in- 
stall than  a  chimney,  so  the  whole  question  revolves  around 
the  point  of  operating  expense.  In  connection  with  a  con- 
tinuous kiln,  the  chimney  is  not  as  cheap  to  operate  as  at 
first  appears.  A  chimney  is  always  affected  by  atmospheric 
conditions,  sometimes  to  the  point  where  the  fire  scarcely 
moves,  while  with  a  fan  a  constant  speed  can  be  maintained 
under  all  weather  conditions.  A  chimney  always  limits  the 
kiln  to  a  certain  burning  speed  even  under  the  best  conditions. 
With  a  fan  this  "best  chimney  speed"  can  be  increased  from 
hity  to  one  hundred  per  cent.  As  the  conduction  and  radia- 
tion losses  on  a  kiln  are  practically  constant  under  all  operat- 
ing conditions,  this  increased  need  reduces  the  proportionate 
heat  loss.  Also,  with  a  fan,  the  waste  gases  can  be  exhausted  at 
temperatures  of  from  50  degrees  C.  to  75  degrees  C.  when 
the  kiln  has  a  watersmoking  arrangement,  while  for  maximum 
efficiency  the  mean  temperature  of  the  gases  in  a  stack  must 
be  maintained  at  300  degrees  C.  This  means  that  the  exhaust 
gases  at  the  base  of  the  stack  must  be  kept  at  from  400  de- 
grees C.  to  500  degrees  C.  to  allow  for  cooling  as  they  rise 
to  the  outlet.  It  will  be  seen  that  this  item  in  itself  is  worthy 
of  consideration  and  goes  a  long  way  towards  overcoming 
the  cost  of  fan  operation. 

The  size  of  the  fan  is  very  important.  Small  fans  should 
always  be  avoided  on  account  of  the  high  speed  required.  It  is 

141 


142     Clay  Plant  Construction  and  Operation 

* 

much  more  economical  to  install  a  large  unit  that  can  be  oper- 
ated at  a  low  speed  because  the  power  required  increases  as 
the  cube  of  the  speed,  which  means  that  when  speed  is  doubled, 
the  power  required  is  multiplied  eight  times. 

FAN  SHOULD  HAVE  COPPER  BLADES 

The  best  type  of  fan  for  continuous  kiln  work  is  the  over- 
hung induced  draft  or  suction  type.  The  fans  should  always 
have  copper  blades  and  cast  iron  arms.  Sheet  iron  blades  and 
mild  steel  arms  are  eaten  away  so  quickly  by  the  gases  that 
they  are  practically  useless.  Even  heavy  copper  blades  re- 
quire replacing  every  three  or  four  seasons.  Two  fans 
should  always  be  provided  to  prevent  shut-downs.  High 
speed  engines  or  motors  require  repairs,  belts  will  break  and 
bearings  burn  out,  but  the  kiln  must  be  kept  running,  and  it 
can  only  be  kept  running  if  an  auxiliary  fan  is  ready  for 
instant  use.  When  electric  power  is  available  on  a  steam 
operated  plant  it  is  a  splendid  plan  to  have  one  fan  motor- 
driven,  and  one,  engine-driven.  In  such  a  case  it  is  almost 
impossible  to  have  the  kiln  down  for  more  than  a  few  minutes 
at  a  time.  On  electrically  driven  plants  variable  speed  mo- 
tors should  always  be  provided  for  the  fans.  The  control 
such  motors  give,  makes  it  almost  unnnecessary  to  handle  the 
clampers  in  order  to  regulate  the  draft.  Also  the  results  are 
more  positive  when  the  draft  is  regulated  by  the  fan  speed. 

The  fans  should  be  covered  with  a  brick  housing,  as  a 
steel  housing  is  quickly  destroyed  by  the  gases.  In  building- 
such  a  housing,  provision  should  be  made  for  examining  the 
fan  from  time  to  time  and  also  removing  it  for  repairs. 

Even  when  using  a  fan,  a  discharge  stack  is  necessary. 
Such  stacks  should  be  high  enough  to  carry  the  gases  well 
above  the  yard.  When  the  stacks  are  low  the  waste  gases 
drifting  thru  the  yard  and  buildings  will  often  seriously  inter- 
fere with  the  work  of  the  men. 

SOME  POINTS  REGARDING  ROOF  CONSTRUCTION 

Practically  all  continuous  kilns  are  provided  with  roofs. 
These  vary  from  the  flimsiest  kind  of  a  shed  structure  to  the 
best  type  of  steel  construction.  The  kiln  roof  presents  a 
problem  that  is  well  worth  a  little  of  the  clayworkers'  con- 
sideration. It  must  be  remembered  that,  as  a  rule,  they  are 
large  affairs,  a  double  battery  kiln  of  fifty  thousand  daily 
capacity  requiring  a  roof  measuring  approximately  one  hun- 
dred and  twenty-five  by  two  hundred  feet;  that  they  are  gen- 
erally a  bad  fire  risk;  are  subject  to  a  lifting  wind  pressure 


Hoof  and  Producer  House  Construction  143 

due  to  their  not  being  protected  by  side  walls ;  are  exposed 
to  the  ordinary  wind  pressure  and,  in  many  instances,  to 
very  heavy  snow  loads.  Consideration  must  also  be  given 
to  the  fact  that  the  roof  is  subject  to  the  radiation  from  the 
kiln.  When  built  of  green  lumber,  this  heat  will  draw,  strain 
and  twist  the  trusses  and  timbers  to  such  an  extent  that  the 
roof  is  unable  to  withstand  the  hard  service  put  upon  it  and 
collapses  or  partially  collapses  during  a  high  wind  or  under 
a  heavy  snow  load. 

There  is  little  question  but  that  men  of  experience  will 
agree  that  the  wooden  roof  is  to  be  condemned.  Generally, 
its  size  and  weight  compels  the  use  of  heavy,  uneconomical 
trusses  which  have  a  tendency  to  weaken  under  their  own 
weight.  Considering  the  cost  of  lurrfber,  the  high  insurance 
rate  or  the  inability  to  get  insurance,  and  the  upkeep,  the 
steel  frame,  metal-covered  roof  is  little,  if  any,  more  ex- 
pensive in  the  end. 

DO   NOT  BUILD   DOUBLE   HIP  ROOFS 

In  the  case  of  the  double  battery  kiln  it  has  been  the  custom 
to  build  roofs  of  the  double  or  triple  hip  design.  Such  roofs 
should  be  avoided  for  several  reasons.  They  are  more  ex- 
pensive to  construct  because  they  require  more  material :  the 
valleys  between  the  hips  collect  and  hold  large  quantities  of 
snow,  and  it  is  almost  impossible  to  so  construct  them  that 
the  water  from  melting  snow  and  from  rain  will  not  leak 
onto  the  kiln  to  a  greater  or  less  extent  after  the  roof  is  a 
few  years  old.  It  is  by  far  the  best  plan  to  construct  the  roof 
with  a  single  ridge,  no  matter  what  the  span  may  be,  for 
the  same  number  of  supports  can  be  used  for  the  trusses  a» 
in  any  other  type. 

When  wooden  roofs  arc  built,  great  care  should  be  taken 
to  have  the  trusses  high  enough  above  the  top  of  the 
kiln  to  avoid  the  danger  of  fire.  Care  must  also  be  taken  to 
avoid  placing  trusses  or  other  timber  work  near  the  vents  in 
the  crown  or  crowns  or  near  other  parts  of  the  kiln  which  be- 
come very  hot.  The  exposed  gas  flues  on  a  gas  fired  kiln  are 
one  of  the  points  that  must  be  watched  in  this  respect  as  they 
get  very  hot  during  "burnouts." 

When  constructing  a  producer-gas-fired  kiln  it  is  neces- 
sary to  provide  a  building  for  the  housing  of  the  gas  pro- 
ducers, and  it  will  be  well  to  bear  in  mind  the  fact  that  this 
is  one  of  the  important  parts  of  the  plant.  Up  to  very  recently 
it  was  the  custom  to  merely  cover  the  producers  with  a 
wooden  roof,  the  duty  of  which  was  to  protect  the  operators 


144     Clay  Plant  Construction  and  Operation 


Roof  and  Producer  House  Construction  145 


146     Clay  Plant  Construction  and  Operation 

from  the  weather.  In  the  past  few  years,  however,  the  effi- 
cient manufacture  of  the  gas  has  been  given  considerable 
thought  and  study  by  a  few  of  those  interested  in  the  subject, 
and  the  result  has  been  the  evolution  of  a  modern  gas  plant 
adapted  to  clay  plant  work. 

To  suit  the  majority  of  cases  it  was  realized  that  such  a 
plant  must  involve  the  least  possible  expenditure  of  money 
coupled  with  the  greatest  possible  efficiency. 

The  building  itself  should  be  strong,  as  nearly  fireproof  as 
possible,  well  lighted,  well  ventilated  and  should  have  sufficient 
space  for  proper  working  conditions. 

The  "clean  out"  floor  should  be  so  arranged  as  to  leave  at 
least  eight  feet  clear  around  each  producer.  This  is  necessary 
on  account  of  the  use  of  long  bars  for  breaking  down  clinker 
thru  the  cleaning  doors,  and  the  fact  that  men  cannot  work 
too  close  to  the  open  doors  in  hot  weather.  The  water  pans 
or  seals  should  be  set  up  on  the  floor  like  a  saucer  and  not 
buried  so  that  the  rim  comes  level  with  the  floor  as  is  often 
done.  Setting  them  up  makes  it  much  easier  for  the  men  to 
pull  clinkers  from  under  the  producer  and  makes  the  removal 
of  clinker  from  the  pans  much  easier  and  quicker. 

BLAST    PIPE    CONNECTION     SHOULD     BE    ACCESSIBLE 

A  man-hole  and  tunnel  should  be  provided  at  each  pro- 
ducer giving  access  to  the  blast  pipe  connection  with  the 
grate.  It  is  possible  for  the  blast  pipe  to  become  choked  and, 
if  it  is  inaccessible,  the  producer  must  be  shut  down  and  em- 
ptied before  repairs  can  be  made  or  else  an  excavation  must 
be  made  under  the  producer. 

The  blower  pits  should  be  in  a  well-lit,  accessible  location. 
Each  pit  should  be  built  so  as  to  allow  a  man  to  get  down 
into  it  and  make  repairs.  All  connections  between  blower 
and  grate  which  are  placed  underground  and  are  inaccessible, 
should  be  made  of  sewer-pipe.  To  bury  light  metal  pipes 
underground  leads  to  troublesome  and  expensive  repairs. 

Each  blower  should  be  provided  with  a  steam  gauge  and  a 
draft  gauge,  and  the  main  steam  line  from  the  boiler  should 
be  provided  with  a  regulating  valve  to  insure  constant  pres- 
sure. Each  pit  should  also  be  provided  with  a  steam  jet  or 
ejector  for  keeping  the  condensation  down  to  the  proper 
level.  Fig.  70  shows  the  arrangements  described  above. 

AVOIDING    SHUT    DOWNS   FOR    BURNING   OUT 

During  the  operation  of  a  gas  plant  the  greatest  accumula- 
tions of  soot  and  tar  are  found  in  the  main  gas  flue  just 


Hoof  and  Producer  House  Construction  147 


oiO 

U_ 


148     Clay  Plant  Construction  and  Operation 

beneath  the  points  where  the  "down  takes"  from  each  pro- 
ducer enter  this  flue.  This  accumulation  chokes  off  the  gas 
supply  and  occasions  frequent  shut-downs  for  burning  out. 
A  way  of  avoiding  this  trouble  by  providing  a  method  for 
cleaning  out  the  flue  is  shown  in  Fig.  71. 

Under  each  "down  take"  is  built  a  chamber  which  opens  by 
means  of  wickets  into  the  clean  out  floor  of  the  producer 
house.  The  accumulating  soot  and  tar  falls  into  the  upper 
part  of  this  chamber  onto  an  iron  plate.  As  soon  as  a  suffi- 
cient quantity  has  accumulated  to  interfere  with  the  gas  flow 
in  the  flue,  the  plate  is  pulled  out  and  the  soot  and  tar  falls 
into  the  lower  part  of  the  chamber.  The  plate  is  then  re- 
placed and  the  lower  wicket  opened  for  the  removal. 

The  main  gas  flue  should  never  be  tied  into  or  bwlt  tight 
against  the  wall  of  the  producer  house.  If  this  is  done  the 
expansion  of  the  flue  will  either  wreck  itself  or  the  wall.  A 
cinder  cushion  should  be  provided  between  the  flue  and  the 
wall  to  take  the  pressure. 

All  window  openings  on  the  cleanout  floor  should  be  near 
the  ceiling  to  allow  for  the  easy  escape  of  gas  and  heat  dur- 
ing the  cleaning  of  the  producers. 

The  floor  of  the  charging  room  should  be  fireproof  and  cap- 
able of  carrying  a  load  of  at  least  twenty-five  tons  for  each 
producer.  Shipments  of  coal  cannot  always  be  regulated  and 
it  is  well  to  provide  for  ample  storage  to  prevent  expensive 
rehandling  of  fuel.  Comparatively,  so  little  fuel  is  required 
on  the  average  plant  that  it  scarcely  pays  to  consider  auto- 
matic feeding  hoppers  above  each  producer.  However,  a  coal 
unloading  device  consisting  of  a  track  hopper,  elevator  and 
conveyor,  which  will  drop  the  fuel  beside  each  producer,  is 
an  investment  worth  consideration.  Its  value  will  depend, 
however,  upon  the  size  of  the  plant.  The  same  sort  of  outfit 
should  also  be  considered  in  connection  with  a  coal-fired  kiln, 
except  in  this  case,  the  fuel  would  be  conveyed  to  the  top  of 
the  kiln.  To  say  the  least,  handling  coal  by  hand  from  the 
modern  hopper  bottom  coal  car  to  a  point  above  the  car's  sides 
is  a  difficult,  nasty  job  and  some  kind  of  mechanical  han- 
dling has  become  almost  essential. 

Care  should  be  taken  to  have  the  roof  of  the  charging  room 
high  enough  to  allow  for  the  use  of  the  long  pokers  which  are 
necessary.  These  pokers  are  nearly  as  long  as  the  producers 
are  high,  and  the  roof,  therefore,  at  the  point  above  the  poke 
holes,  should  be  somewhat  higher  than  this  dimension, 
especially  as  the  pokers  have  to  be  handled  with  a  block  and 
tackle. 


Roof  and  Producer  House  Construction  149 

A  monitor  should  be  built  the  entire  length  of  the  roof  to 
allow  for  the  escape  of  gas. 

SMALL    PRODUCERS    BETTER    THAN     LARGE    ONE 

In  determining  the  size  of  the  producer  to  use  it  should  be 
remembered  that  two  small  ones  give  far  better  results  than 
one  large  one,  or  four  small  ones  better  results  than  two  large 
ones.  The  small  producer  is  much  easier  to  handle  in  every 
way,  and  the  greater  the  number  of  producers  used,  the 
more  even  is  the  gas  flow.  The  fuel  consumption  is  more 
likely  to  be  lower  on  a  number  of  small  producers  than  on  a 
few  large  ones  because  there  is  not  the  tendency  to  push  the 
small  ones  in  order  to  maintain  the  flow  of  gas.  As  one 
man  can  look  after  six  six-foot  producers  without  trouble, 
there  is  no  labor  to  be  saved  by  putting  in  a  smaller  number 
of  large  producers.  In  fact,  there  are  some  plants  which  are 
operating  two  nine-foot  producers  which  require  two  and 
sometimes  three  men  on  each  shift,  while  others  are  operating 
five  six-foot  producers  with  one  man,  and  doing  it  easily. 

As  the  design  of  gas  producers  has  become  a  specialized 
branch  of  engineering,  it  is  by  far  the  best  policy  to  -have 
some  company,  specializing  in  this  line,  furnish  producers 
when  required.  Each  coal  has  its  own  peculiarities  and  there 
is  no  producer  made  which  will  give  satisfactory  service  in 
all  cases,  and  certainly  no  one  who  has  not  had  very  wide 
experience  with  different  kinds  of  coal,  is  competent  to  design 
a  producer  for  a  plant  where  the  number  of  different  coals 
available  are  limited.  It  is  possible,  however,  for  experts  to 
design  successful  producers  for  any  kind  of  service,  whether 
the  fuel  be  wood,  peat,  lignite,  anthracite,  or  clean  or  dirty 
bituminous  coal. 

Clay  workers  erecting  a  continuous  kiln  of  any  type  should 
always  provide  themselves  with  a  competent  inspector,  and 
this  inspector  should  preferably  be  an  engineer.  Merely  put- 
ting a  man  on  the  job  will  not  do;  he  must  be  a  man  with  ex- 
perience in  masonry  construction  and  engineering  problems. 
Men  of  this  kind  are  not  easy  to  obtain  and  are  expensive, 
but  having  one  on  the  job  every  minute  is  as  necessary  as  the 
brick  and  mortar.  It  is  not  so  essential  that  such  an  inspec- 
tor should  have  had  previous  kiln  experience,  altho  this  is  an 
advantage,  but  he  must  know  what  constitutes  good  brick- 
work and  must  be  able  to  straighten  out  the  difficulties  which 
are  certain  to  arise  even  when  the  most  complete  plans  and 
specifications  are  furnished.  An  engineer  often  draws  a  few 
lines  on  paper  which  appear  to  offer  no  difficulties  but  are 


150     Clay  Plant  Construction  and  Operation 

extremely  difficult  to  execute  in  practice.  Lack  of  attention 
to  business,  slow  thinking  and  poor  judgment  on  the  part  of 
incompetent  inspectors  has  cost  many  clayworkers  large  finan- 
cial loss  and  has  resulted  in  many  kilns  being  partial  or  com- 
plete failures.  The  clayworker  should  move  slowly  in  this 
matter  and  should  be  extremely  careful  about  accepting,  with- 
out thoro  investigation,  the  men  recommended  by  kiln 
builders. 

The  foregoing  specifications  for  the  construction  of  con- 
tinuous kilns  are  not  intended  for  the  exclusive  use  of  the 
man  who  wants  a  good  kiln,  but  represent  what  must  be  done 
by  anybody  if  a  kiln  that  will  stand  up  to  its  work  and  pay 
dividends  is  to  result.  A  more  severe  set  of  specifications 
may  be  followed,  but  if  any  attempt  is  made  to  "get  by"  with 
anything  less  rigid,  nothing  but  regret  will  follow. 

THE  RESULT  OF  POOR  CONSTRUCTION 

An  example  of  what  poor  continuous  kiln  construction  can 
do  is  illustrated  in  the  following.  A  large  concern  which 
operates  a  battery  of  down-draft  kilns  and  a  large  continuous 
kiln  unit  on  the  same  plant,  found  that  the  latter  saved  them 
two-thirds  of  the  fuel  and  one-half  of  the  labor  as  compared 
with  the  down-drafts.  However,  after  the  continuous  kiln 
had  been  in  operation  a  few  years  the  repairs  had  become 
so  heavy  that  it  was  necessary  to  make  a  new  comparison  of 
costs.  It  was  then  found  that  in  spite  of  the  saving  in  fuel 
and  labor  which  the  continuous  kiln  effected,  it  had  cost 
twenty-three  cents  per  thousand  brick  more  to  operate  it  than 
the  down-draft  kilns.  Not  only  had  the  saving,  made  by  cut- 
ting off  two-thirds  of  the  fuel  cost  and  half  the  labor  cost, 
been  utterly  wiped  out,  but  twenty-three  cents  per  thousand 
had  been  added.  By  what?  Repairs.  And  this  is  the  tale 
the  cost  sheets  of  many  continuous  kiln  users  would  tell  if 
they  could  but  be  consulted.  As  has  been  already  stated,  the 
men  who  have  built  continuous  kilns  heretofore  have  been 
the  pioneers,  it  is  they  who  have  been  paying  for  the  experi- 
ence which  can  only  be  bought  in  this  way,  and  if  the  builder 
of  the  future  will  not  benefit  by  the  lessons  learned  by  those 
who  have  gone  before,  he  is  simply  courting  disaster. 

It  is  well  to  beware  of  the  man  who  offers  to  build  a  cheap 
kiln  and  also  it  is  well  to  consider  carefully  the  "estimates" 
usually  presented  by  kiln  builders.  When  reliable  informa- 
tion is  wanted  go  privately  to  the  men  who  have  been  operat- 
ing kilns  for  several  years,  and  as  a  general  rule,  it  will  be 
found  that  they  are  only  too  glad  to  help  others  avoid  the  pit- 
falls into  which  they  themselves  unwittingly  fell. 


CHAPTER  XIV 

Operating  a  Coal-Fired  Con- 
tinuous Kiln 


ANY  DESCRIPTION  of  the  operation  of  a  continuous 
kiln  of  any  type  can  only  cover  the  subject  in  a  gen- 
eral way.  Continuous  kilns  of  the  same  type,  as  is  the  case 
with  down-draft  kilns,  differ  radically  in  action,  each  kiln 
having  its  own  peculiarities.  Continuous  kiln  operators  have 
worked  for  months  with  a  kiln,  every  detail  of  which  was 
familiar  to  them,  without  producing  a  single  successful  burn, 
yet  men  with  no  experience  whatever  have,  by  study  and 
close  attention  to  details,  made  the  same  kilns  a  decided  suc- 
cess. The  reason  for  this  is  that  the  men  who  are  usually 
sent  out  to  start  a  new  kiln  follow  certain  set  rules  and 
methods,  while  the  man  with  only  an  elementary  knowledge 
allows  the  kiln  to  make  its  own  regulations — something  it  is 
bound  to  do  in  the  end  if  it  is  to  be  successfully  operated. 

Naturally  the  "standard"  rules  of  procedure  must  be 
followed  in  the  beginning  and  the  necessary  changes  worked 
out  from  them  as  they  are  found  unsuitable.  Radical 
changes  should  not  be  made,  the  better  policy  being  to 
change  gradually. 

In  dealing  with  a  new  kiln  it  must  be  borne  in  mind  that 
it  takes  from  five  to  seven  and,  in  some  cases,  even 
more  complete  rounds  before  normal  operating  conditions 
are  reached.  This  is  due  to  the  large  body  of  masonry 
which  must  be  thoroly  dried  out  and  heated  up,  together 
with  the  drying  out  and  heating  up  of  the  ground  under 
the  kiln.  The  bottoms  usually  give  the  most  trouble  on 
a  new  kiln  and  this  must  be  expected.  It  is  far  more 
economical  to  accept  soft  brick  in  the  bottom  courses  for 
the  first  few  rounds  instead  of  holding  up  the  kiln  and 
using  fuel  in  an  attempt  to  make  them  hard  for,  as  a 
rule,  not  only  is  the  attempt  unsuccessful  but  brick  are 

151 


152     Clay  Plant  Construction  and  Operation 

overburned  on  the  top,  and  the  kiln  acts  badly  because 
of  the  impossibility  of  holding  the  "backing"  heat  for  a 
long  period. 

Slack  is  generally  used  on  all  types  of  coal-fired  continuous 
kilns  and  by  far  the  best  results  can  be  obtained  from  its  use. 
It  is  not  the  best  practice  to  have  the  coal  too  fine,  much 
better  results  being  had  when  it  ranges  from  dust  to  almost 
a  nut  size.  Such  coal  burns  freely  and  is  not  so  likely  to 
cake  at  the  bottom  of  the  fire  shafts. 

BEST    FUELS    RECOMMENDED    FOR    KILNS 

While  the  claim  that  a  continuous  kiln  can  be  operated  on 
very  low  grade  fuels  is  true,  nevertheless,  the  best  and  most 
economical  results  cannot  be  gotten  from  such  fuels.  The 
results  obtained  from  slack,  which  is  high  in  ash  and  low 
in  volatile  matter,  are  not  to  be  compared  with  those  from 
a  high  grade,  clean  slack  and,  as  a  general  rule,  it  does  not 
pay  to  use  the  former  where  the  latter  is  obtainable.  A 
high-grade  fuel  will  not  only  give  greater  burning  speed, 
but  much  less  will  be  used  per  unit  of  ware.  Thus  a  decid- 
ed saving  in  the  cost  of  burning  is  shown  in  nearly  every 
case.  Where  high-grade  ware  is  burned  it  is  decidedly  ad- 
vantageous to  use  a  fuel  low  in  ash.  The  draft  carries  the 
ash  and  scatters  it  over  the  ware  and,  if  there  is  a  large 
quantity,  much  of  the  ware  may  be  marred  or  spoiled. 

The  setting  of  the  ware  in  a  continuous  tunnel  kiln  is, 
with  little  question,  the  most  important  point  in  the  opera- 
tion. On  it  depends  to  a  great  extent,  not  only  the  speed, 
but  the  quality  of  the  resulting  ware,  and  the  fuel  con- 
sumption. Many  kilns  which  would  have  given  good  results 
have  been  condemned  as  failures  thru  the  ignorance  shown 
m  this  department. 

The  setting  in  this  type  of  kiln  differs  from  all  others  be- 
cause the  fire  and  draft  moves  in  the  direction  of  the  length 
of  the  kiln.  In  other  words,  the  draft,  instead  of  being  up 
or  down,  is  horizontal. 

Being  generated,  to  a  great  extent,  on  or  near  the  floor, 
the  heat  has  a  natural  tendency  to  rise  to  the  crown  and 
this  tendency  can  only  be  overcome  by  so  arranging  the 
setting  that  freer  flow  is  given  near  the  floor,  while  at  the 
same  time  the  draft  is  baffled  by  tighter  setting  towards  the 
top.  These  conditions,  coupled  with  the  necessity  for  pro- 
viding firing  or  fuel  shafts  in  the  setting,  and  also  the  neces- 
sity for  counteracting  the  pull  of  the  draft  connections  on 
one  side  of  the  tunnel,  make  the  setting  a  difficult  and  intricate 


Coal-Fired  Continuous  Kiln 


153 


problem.  In  fact,  setting  ware  in  a  tunnel  kiln  is  in  a  class 
by  itself,  and  requires  considerable  skill  and  head  work  if 
the  best  results  are  to  be  obtained. 

TUNNEL    KILN     BEST    ADAPTED    TO    CRUDER    WARES 

The  tunnel  kiln  is  really  best  adapted  to  burning  the  com- 
moner grades  of  ware,  in  which  clear  color  and  flame  flash 
are  of  little  importance.  However,  it  is  successfully  used 


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c 


JLP 


for  high-grade  products.  In  such  cases,  special  care  must 
be  taken  to  protect  the  faces  or  sides  to  be  exposed  when 
in  use,  from  the  flame,  flying  ash  and  fuel. 

Setting  plans  are  usually  furnished  with  a  new  kiln,  and  a 


154     Clay  Plant  Construction  and  Operation 

skilled  setter  is  often  furnished  to  start  the  work  off  right, 
but  as  every  kiln  develops  its  own  peculiarities,  the  standard 
setting  plan  is  seldom  followed,  entirely,  for  any  length  of 
time. 

THE   MANNER  OF  SETTING   RACE  FLUES 

The  race  flues  or  trace  holes,  as  the  flues  running  along  the 
floor  and  parallel  to  the  length  of  the  kiln  are  called,  are 
variously  set  from  two  to  eight  brick  high  and  are  from  four 
to  eight  inches  wide.  Their  number  is  governed  by  the  num- 
ber of  feed  holes  across  the  tunnel.  No  standard  size  can 
be  laid  down  for  these  flues,  as  they  are  governed  by  the 
amount  of  ash  in  the  fuel,  the  draft,  the  kind  of  ware  being 
burned,  the  setting  above  them,  and  the  general  conditions 
under  which  the  kiln  is  operated.  The  low,  wide  flues  are 
recommended,  as  they  do  not  complicate  the  setting  as  much 
as  the  high,  narrow  ones. 

As  there  is  always  a  tendency  for  the  heat  to  travel  faster 
in  the  middle  race  flues,  it  is  sometimes  necessary  to  have 
the  outside  flues  higher  and  sometimes  wider  than  those  in  the 
center.  In  kilns  with  the  tunnel  continuing  around  the  ends, 
it  is  necessary  to  vary  tne  size  of  these  flues,  making  the  one 
nearest  the  inner  wall  the  smallest  and  gradually  increasing 
the  size  towards  the  outer  wall.  This  prevents  the  gases 
from  short-cutting-  thru  the  shortest  flues  as  they  would  do 
unless  forced  to  take  the  longer  route.  Fig.  72  shows  various 
methods  of  setting  race  flues. 

Soft  bottoms,  one  of  the  common  difficulties  of  the  tunnel 
kiln,  are  due  in  many  cases  to  the  size  of  the  race  flues. 
When  too  large,  the  cooler  air  has  a  tendency  to  run  along 
the  bottom  thru  these  flues,  thereby  keeping  the  bottom 
courses  chilled.  This  difficulty  is  often  overcome  by  merely 
reducing  the  size  of  these  flues.  When  using  coals  which  are 
high  in  ash,  care  must  be  taken  to  provide  sufficient  height 
to  prevent  their  becoming  choked  and  thereby  preventing  suffi- 
cient air  from  reaching  the  fires  ahead. 

A    GUIDE    HELPS    IN    LOCATING    THE    FLUES 

Unless  the  setters  are  skilled  in  continuous  kiln  work  it  is 
wise  to  provide  a  guide  for  locating  the  race  flues  in  order 
to  keep  them  straight.  A  guide  consists  of  a  board  of  a 
length  equal  to  the  width  of  the  tunnel,  with  the  correct  loca- 
tion of  the  race  flues  marked  upon  it.  It  is  quite  important 
that  the  race  flues  be  kept  perfectly  straight.  Kinks  and 
projecting  brick  interfere  with  the  draft  and  make  it  impos- 
sible to  standardize  the  kiln  operation. 


Coal-Fired  Continuous  Kiln 


155 


In  determining  the  best  type  of  fire  shaft  to  use  in  a  kiln, 
three  factors  must  be  taken  into  consideration :  First,  the  size 
of  the  fuel  to  be  used,  whether  very  fine  or  very  coarse 
slack;  second,  the  quality  of  the  fuel,  whether  high  or  low 
in  ash  and  whether  caking  or  non-caking;  third,  the  kind  of 
ware  being  burned,  whether  common  and  not  effected  by  the 
flame  flash  and  ash,  or  high  grade  and  likely  to  be  culled  by 
flashing  and  ash. 

The  coarse  grades  of  fuel  usually  burn  faster  than  the 
finer  grades  (unless  dust  is  used),  and  there  is,  therefore, 
less  likelihood  of  their  heaping  up  and  caking  and  thereby 
choking  the  draft  in  the  race  flues.  They  also  have  a  ten- 
dency to  distribute  themselves  thru  the  length  of  the  shaft 
better  than  the  finer  grades.  For  these  reasons  it  is  pos- 
sible to  set  much  simpler  fire  shafts  when  course  fuels  are 
used.  See  Fig.  73. 

AN    ADVANTAGE    OF    NON-CAKING    FUEL 

When  non-caking  fuel  is  used  it  is,  of  course,  possible 
to  allow  more  of  it  to  drop  to  the  bottom  of  the  shaft  with- 
out getting  into  difficulties  with  the  draft,  but  when  caking 


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Fig.    73.      Method    of   Setting    Firing    Shafts. 

coal  is  used,  whether  fine  or  coarse,  provision  must  be 
made  to  allow  it  to  lodge  at  various  points  in  the  shaft. 
When  fuels  high  in  ash  are  used,  and  it  is  desired  to  have 
as  few  pieces  of  ware  as  possible  spoiled  by  the  ash,  the 
shaft  must  be  set  so  that  as  few  lodging  places  as  possible 


156     Clay  Plant  Construction  and  Operation 

are  provided,  but  at  the  same  time  enough  so  that  the  race 
flues  will  not  become  blocked  up  by  the  accumulation  at  the 
bottom. 

When  high-grade  ware  is  being  burned  it  is  desirable  to 
have  as  little  contact  between  th*e  ware  and  fuel  as  possible. 
This  condition  requires  the  fuel  to  be  burned  at  the  bottom. 
In  cases  where  conditions  prohibit  such  practice,  common 
ware  is  set  around  the  fire  shafts  or  the  ware  which  is 
set  around  the  shafts  is  accepted  as  common  or  low-grade. 

Combinations  of  the  above  conditions,  of  course,  occur  quite 
frequently,  so  that  it  is  more  often  than  not  a  case  of  experi- 
menting until  the  most  suitable  method  of  setting  the  shafts 
is  found. 

Guides  for  setting  the  firing  shafts  are  necessary  if  the 
best  results  are  to  be  had.  These  guides  are  dropped  thru 
the  feed  holes  in  the  crown  and  extend  to  the  Moor.  They 
are  removed  thru  the  holes  when  the  shaft  is  completed. 
Shafts  must  always  be  set  so  that  a  clear  view  of  the  bot- 
lom  can  be  had  from  the  feed  hole. 

The  setting  of  the  benches  depends  to  a  considerable  extent 
upon  the  draft  Vised.  The  movement  of  the  draft  in  a  hori- 
zontal direction  always  has  a  tendency  to  overcome  the  dis- 
position of  the  heat  to  rise  from  the  bottom.  Therefore,  the 
stronger  or  higher  the  draft,  the  greater  will  be  the  concen- 
tration of  heat  near  the  bottom,  and  vice  versa.  This  makes 
it  necessary  to  set  the  ware  tight  at  the  botton  and  looser 
towards  the  top  when  high  draft  is  used,  in  order  to  baffle 
the  drift  of  the  heat  along  the  bottom  and  force  it  to  the 
top.  In  case  a  low  draft  is  used,  the  ware  should  be  set 
looser  at  the  bottom  with  a  gradual  tightening  as  it  approaches 
the  crown.  There  are,  of  course,  many  intermediate  stages 
between  the  high  and  low  extremes,  but  in  each  case  the  result 
to  strive  for  is  a  heat  balance  over  the  entire  cross-section 
of  the  tunnel,  in  order  to  get  perfect  heat  distribution.  Ex- 
periment alone  will  determine  the  best  method  for  each  kiln. 

WARE   SHOULD   ALWAYS    BE  SET   UP  TO  CROWN 

In  a  tunnel  kiln  the  ware  should  always  be  set  up  to  the 
crown,  otherwise  much  of  the  heat  will  travel  along  over 
the  ware,  with  consequent  loss  of  burning  efficiency.  The 
drop  arches  take  care  of  this  difficulty  after  the  ware  settles 
and  for  this  reason  they  should  be  kept  in  good  condition  and 
the  brick  set  tightly  against  them. 

Two   things   to  be  constantly  borne  in   mind   are,   that   the 


Coal-Fired  Continuous  Kiln  157 

heat  must  be  kept  ahead  in  the  bottom;  and  that  it  does  not 
pay  to  attempt  to  crowd  the  ware  in  a  continuous  kiln.  Set- 
ting too  close  invariably  increases  the  cost  thru  the  slowing 
up  of  the  fire  travel.  On  the  other  hand,  if  the  setting  is  too 
open,  trouble  will  result  from  admission  of  too  much  air  into 
the  first  zone,  and  thru  the  premature  loss  of  "backing"  heat. 

PAPER  PARTITIONS  SHOULD  BE  PLACED  WITH  CARE 

The  lack  of  care  in  applying  the  paper  partitions  at  the 
end  of  each  section  often  results  in  poor  operation.  It  is 
quite  a  difficult  matter  to  put  on  a  good  air-tight  partition, 
but  it  can  be  done.  It  is  a  good  plan  to  train  a  careful  man 
to  do  this  work  and  put  the  responsibility  on  him.  Ordinary 
flour  paste  will  answer  the  purpose  but  it  must  be  kept  fairly 
thick.  The  paper  must  be  of  a  kind  that  will  not  lose  its 
strength  when  dampened  by  the  moisture  of  the  water- 
smoking  period.  In  other  words,  it  is  best  to  use  a  paper  that 
is  as  near  waterproof  as  possible,  but  at  the  same  time  one 
that  is  not  so  heavy  and  stiff  as  to  make  it  impossible  to  paste 
it  to  the  brick. 

Rats  and  mice  are  frequently  numerous  around  a  clay  plant 
and  these  rodents  are  often  the  cause  of  considerable  con- 
tinuous kiln  trouble.  This  is  due  to  their  eating  the  paper  in 
order  to  get  the  flour  paste,  and  in  this  way  causing  draft 
troubles  which  are  hard  to  locate.  Copper  sulphate  or  othe~ 
poisons  should  be  dissolved  in  the  paste,  in  such  cases,  or  a 
cat  trained  to  make  its  headquarters  at  the  kiln. 

Many  tunne!  kilns  are  not  provided  with  water-smok- 
ing arrangements,  the  watersmoking  being  accomplished  by 
drawing  the  combustion  gases  thru  the  last  section  set,  before 
exhausting  them  into  the  draft  flue.  In  such  cases  scum- 
ming trouble  is  practically  a  certainty.  The  combustion 
gases  always  contain  considerable  sulphur  trioxide  and  sul- 
phuric acid,  and  these,  when  they  come  into  contact  with 
the  moist,  cool  ware,  cause  the  formation  of  scum  or  "white- 
wash." It  is  for  this  reason  that  so  much  ware  that  is 
burned  in  this  type  of  kiln  is  discolored  and  unsightly. 

When  the  kiln  has  no  special  arrangement  for  water- 
smoking,  the  only  precaution  necessary  at  this  period  is  to  be 
sure  that  the  temperature  of  the  gases  which  are  admitted 
into  a  freshly  set  section  is  not  too  high,  or  in  other  words, 
that  the  setters  are  not  too  close  to  the  fire.  With  some  clays 
it  is  possible  to  admit  the  gases  at  temperatures  of  200  de- 
grees Fahr.  or  over,  but  with  others  it  is  not  safe  to  use  them 


158     Clay  Plant  Construction  and  Operation 

when  over  100  degrees  Fahr.  at  the  beginning.  This  can  be 
regulated  by  the  number  of  sections  ahead  of  the  fire,  as  the 
greater  the  number  of  sections  the  gases  travel  thru,  the 
cooler  they  become. 

WATERSMOKING   SIMPLE    WITH    SPECIAL    FLUES 

When  watersmoking  flues  are  provided,  the  operation  of 
watersmoking  is  quite  simple.  It  consists  of  connecting  the 
flue  to  a  section  behind  the  fire  which  has  still  a  temperature 
of  from  200  degrees  Fahr.  to  500  degrees  Fahr.,  and  then 
making  a  connection  with  the  section  to  be  watersmoked.  The 
connection  with  the  main  draft  flue  is  then  opened  and  the 
pure  hot  air  is  drawn  thru  the  ware.  Naturally  the  paper  par- 
titions at  each  end  of  the  watersmoking  section  are  kept  intact 
until  the  period  is  completed.  In  this  way  the  draft  is  con- 
trolled independently  of  the  sections  under  fire.  In  order  to 
control  the  temperature^ of  the  hot  air  entering  the  section, 
provision  is  made  for  the  admission  of  cold  air  into  the  water- 
smoking  flue  in  any  desired  quantity. 

As  kilns  are  generally  designed  so  as  to  provide  for  an  ad- 
vance of  one  section  per  day,  it  is  usual  to  complete  the  water- 
smoking  in  twenty-four  hours.  It  is  seldom  possible  and 
often  difficult  in  this  length  of  time  to  get  the  ware  to  a  tem- 
perature much  above  200  degrees  Fahr.  or  225  degrees  Fahr. 
thruout,  but  whatever  the  temperature  may  be  when  the 
period  is  up,  the  partition  nearest  the  fire  is  broken  and  the 
section  thus  connected  up  with  the  burning  section.  The 
watersmoking  flue  connections  are  then  advanced  one  section 
at  each  end. 
SUCCESSFUL  WATERSMOKING  DEPENDS  UPON  DESIGN 

Successful  watersmoking  in  a  tunnel  kiln  depends  very 
largely  on  the  design.  Some  kilns  are  designed  in  such  a 
way  as  to  make  it  almost  impossible  to  get  the  proper  dis- 
tribution of  heat  in  this  period.  Often  too,  the  construc- 
tion of  the  watersmoking  flues  is  so  bad  that  sufficient  heat 
cannot  be  drawn  thru  them  because  of  air  leaks,  and  the  re- 
sult is  that  the  section  has  to  be  taken  into  the  circuit  before 
the  period  is  complete,  with  the  result  that  the  ware  is  al- 
ways "scummed." 

The  use  of  wicket  fires  (temporary  fire-boxes  built  in  the 
wickets)  is  sometimes  resorted  to  in  the  watersmoking  period. 
These  fires  are  fed  with  wood,  coke  or  coal,  and  are  made  to 
carry  the  section  as  far  along  as  possible,  or  to  augment  the 
heat  from  the  watersmoking  flue. 

When  connecting  up  a  section  that  has  been  watersmoking 


Coat-Fired  Continuous  Kiln          159 

to  the  sections  under  fire,  it  is  best  to  split  the  draft  for  a 
certain  period.  Instead  of  closing  the  connection  between 
the  section  behind  the  watersmoked  section  and  the  draft  flue, 
and  drawing  all  of  the  gases  thru  the  watersmoked  section, 
the  draft  connections  of  both  sections  are  partially  opened, 
thus  splitting  the  draft.  If  the  gases  in  the  burning  section 
are  very  hot,  this  method  reduces  the  shock  to  the  ware  in 
the  new  section.  As  the  temperature  is  raised  in  this  sec- 
tion, however,  its  draft  connection  is  gradually  opened  wider 
while  the  one  in  the  section  behind  is  gradually  closed.  This 
operation  is  continued  until  all  of  the  draft  is  taken  thru  the 
new  section.  With  some  clays  such  precautions  are  unneces- 
sary and  in  such  cases  the  change  may  be  made  abruptly. 

PAPER  PARTITION  SHOULD  NOT  BURN  PREMATURELY 

The  gases  of  the  burning  sections  should  never  be  hot 
enough  to  burn  the  paper  partition  of  the  watersmoking  sec- 
tion until  after  the  watersmoking  is  completed.  If  such  is 
the  case,  the  kiln  is  not  being  operated  economically,  the  waste 
gases  being  discharged  at  too  high  a  temperature.  When  the 
setting  is  held  up  for  any  reason,  the  burning  must  also  be 
slowed,  and  if  necessary,  stopped  completely.  A  continuous 
kiln  loses  heat  very  slowly  and  firing  may  be  stopped  for 
from  two  to  five  weeks  and  there  will  still  remain  enough 
heat  to  ignite  fuel  when  operations  recommence. 

There  is  always  considerable  discussion  as  to  the  num- 
ber of  sections  of  a  kiln  that  should  be  kept  under  fire, 
and  as  to  the  number  of  sections  the  draft  should  be 
pulled  thru  before  being  exhausted.  It  is  small  wonder 
that  no  agreement  can  be  reached  on  these  questions,  and 
small  wonder  also  that  one  who  attempts  to  give  advice 
on  the  subject  can  seldom  be  of  very  much  service.  As 
has  been  said  before,  it  is  seldom  that  two  kilns  are  found 
that  work  alike,  and  when  the  difference  in  construction, 
clays,  ware,  setting,  size  of  fans  or  stacks,  condition  of  the 
kilns,  and  operators  are  considered,  it  is  not  to  be  expected. 
It  is  possible,  therefore,  to  cover  the  subject  of  burning 
in  a  general  way  only,  taking  a  sort  of  average  of  general 
existing  conditions. 

NUMBER  OF  SECTIONS  TO   KEEP   UNDER   FIRE 

Fuel  should  be  fed  to  from  three  to  five  sections.  The 
high  fire  section  naturally  consumes  the  greatest  quantity, 
and  as  a  rule,  light  charges  should  be  fed  every  ten  to 
twenty  minutes.  The  feed  holes  ahead  and  behind  the  high 


160     Clay  Plant  Construction  and  Operation 

fire  are  fed  lighter  charges  and  at  wider  intervals,  accord- 
ing to  their  distance  from  the  high  fire  and  according  to 
the  speed  with  which  the  fuel  is  consumed,  and  the  sort 
of  clay  used.  Usually  a  section  is  under  high  fire  until  the 
finishing  heat  is  reached,  top  and  bottom,  and  then  a  soak- 
ing heat  is  maintained  for  a  certain  period  until  the  ware 
is  finished.  During  this  period  the  finishing  heat  is  ad- 
vanced. The  whole  operation,  of  course,  is  a  continuous 
one,  the  peak  of  the  temperature  curve  slowly  advancing 
all  the  time. 

As  the  fire  advances,  fuel  is  fed  to  fresh  rows  of  feed 
holes,  but  this  should  never  be  done  until  a  red  heat  shows 
in  the  bottom,  and  fuel  should  only  be  fed  at  such  times 
and  in  such  quantities  as  can  be  entirely  consumed.  Pre- 
mature firing  or  feeding  in  too  large  quantities  will  result 
in  an  accumulation  of  fuel  in  the  race  flues,  with  conse- 
quent checking  of  the  draft,  and  the  possibility  of  too  much 
local  heat  when  the  accumulated  fuel  does  ignite.  It  is 
always  best  to  defer  feeding  fresh  feed  holes  until  a  red 
heat  is  visible,  at  the  bottom,  in  daylight. 

THE     IMPORTANT     MATTER     OF    "BACKING"     HEAT 

It  is  sometimes  necessary  to  feed  fuel  to  several  rows 
of  feed  holes  behind  those  which  are  at  finishing  heat,  in 
order  to  maintain  what  is  known  as  the  "backing."  A  con- 
tinuous kiln,  in  order  to  work  efficiently,  must  have  pre- 
heated air  for  combustion.  This  preheated  air  is  furnished 
by  passing  the  air  required  for  combustion  thru  the  ware 
that  has  been  burned.  In  this  way,  not  only  is  a  large 
percentage  of  the  heat  recovered  and  reused,  but  the  air 
reaches  the  high  fire  section  at  a  temperature  only  a  little 
below  the  temperature  required  to  finish.  It  is  for  this  rea- 
son principally,  that  a  continuous  kiln  uses  only  from  twen- 
ty-five to  thirty-five  per  cent,  of  the  fuel  required  on  a 
periodic  kiln. 

The  amount  of  fuel  required  to  maintain  the  proper  "back- 
ing" depends  largely  upon  how  close  to  the  fire  the  un- 
loaders  work.  If  they  are  very  close,  thru  a  desire  to  rush 
ware  out  of  the  kiln,  a  larger  number  of  rows  will  have  to 
be  kept  under  fire  than  if  a  good  distance  is  kept.  Of  course, 
there  is  a  limit.  The  result  of  working  too  close  is  that  the 
cold  air  rushes  along  the  floor  thru  the  race  flues  and  makes  it 
almost  impossible  to  get  the  bottom  in  the  high  fire  section 
up  to  the  finishing  point,  thus  checking  the  advance.  When 


Coal-Fired  Continuous  Kiln  161 

the  proper  number  of  sections  are  kept  behind  the  fire  it 
is  often  possible  to  stop  feeding  fuel  as  soon  as  the  ware 
has  received  the  proper  amount  of  "soaking,"  there  be- 
ing no  necessity  for  maintaining  a  "backing"  fire  on  ac- 
count of  the  amount  of  hot  ware  thru  which  the  air  must 
pass. 

Wicket  fires  are  used  in  some  kilns  to  assist  the  top 
firing  in  the  high  temperature  zones.  Not  only  do  they  in- 
crease the  burning  speed  to  some  extent,  but  they  insure 
a  well  burned  wicket,  a  point  usually  hard  to  finish  prop- 
erly in  the  average  continuous  kiln.  Wicket  fires  are  usu- 
ally started  in  the  section  ahead  of  the  one  showing  red 
heat  in  the  bottom.  The  fires  are  started  slowly  and 
gradually  brought  up  as  the  ware  will  stand  it.  They  are 
maintained  until  after  the  section  has  passed  the  finishing 
point,  when  the  grates  are  withdrawn  and  the  opening 
bricked  up. 

ECONOMY   OF   WICKET    FIRES  QUESTIONED 

There  is  considerable  question  as  to  the  economy  of 
wicket  fires,  in  spite  of  the  aid  they  give  locally  to  the 
ware  in  the  wicket,  and  the  section  in  general.  As  is  the 
case  with  up  and  down-draft  kilns,  a  considerable  excess 
of  air  is  certain  to  pass  over  the  fires.  The  air  is  not 
preheated,  as  is  the  case  with  the  air  fed  to  the  inside  fires, 
and  consequently,  there  is  a  loss  in  efficiency.  Consider- 
ation must  also  be  given  to  the  ware  damaged  by  contact 
with  the  flame  and  ash  of  these  fires,  there  being  no  bag 
wall  to  protect  it.  Added  to  this  is  the  cost  of  constructing 
these  wicket  fireboxes  and  cleaning  up  the  ash  and  spoiled 
ware  after  them.  These  last  two  items  are  rather  sur- 
prising when  put  down  on  a  cost  sheet. 

DRAFT 

ft  is  practically  impossible  to  designate  the  number  of 
sections  thru  which  the  draft  should  be  pulled  to  get  the 
best  results.  Kilns  equipped  with  stacks  are  definitely  lim- 
ited because  the  stack  can  only  pull  thru  a  certain  number 
of  sections  and  maintain  any  kind  of  speed.  In  this  case 
experiments  must  be  carried  on  to  determine  the  maximum 
number  for  best  results,  and  the  standard  thus  determined 
upon,  should  be  maintained.  When  fans  are  used,  the  size 
of  the  fan  is  one  of  the  determining  factors.  Often  fan 
units  are  far  too  small  for  obtaining  the  best  results,  but  in 


162     Clay  Plant  Construction  and  Operation 

such  cases  it  is  not  so  difficult  to  rectify  matters  as  is  the 
case  where  an  undersized  stack  has  been  built.  An  over- 
size fan  is  a  splendid  investment,  for  it  is  an  easy  matter 
to  cut  the  draft  when  it  is  too  high. 

The  question  of  draft  in  continuous  kiln  operation  is  one 
of  the  greatest  importance.  The  speed  of  the  kiln  is  de- 
pendent to  a  large  extent  upon  it.  There  is  a  surprising 
difference  in  the  rate  of  advance  of  kilns  of  the  same  type 
and  size  which  are  burning  practically  the  same  class  of 
ware.  This  advance  ranges  all  the  way  from  100  to  250 
feet  per  week.  Some  of  this  difference  is  due  to  the  ma- 
terial, but  most  of  it  to  methods  of  operation. 

It  will  be  plain  to  anyone  that  fire  will  travel  at  a  greater 
rate  thru  a  tunnel  under  a  high  draft  than  under  a  low 
one.  It  will  be  just  as  plain  that  fire  will  travel  faster  thru 
loose  setting  than  thru  tight  setting,  and  that  the  gases  can 
be  pulled  thru  the  former  at  a  higher  velocity  than  thru 
the  latter. 

However,  there  is  a  definite  limit  to  the  velocity  that 
may  be  given  to  the  gases  in  a  kiln  by  the  fan  or  stack. 
Kiln  operators  have  all  noticed  that  at  a  certain  point, 
slightly  in  advance  of  the  row  of  feed  holes  receiving  the 
finishing  heat,  there  seems  to  be  no  draft.  When  the  caps 
are  lifted  over  this  point  there  seems  to  be  neither  suction 
nor  pressure,  while  ahead  there  is  suction,  and  behind,  over 
the  high  fire,  there  is  pressure  or  "kick."  Some  operators 
have  also  noticed  that  the  best  results  can  be  obtained  from 
the  kiln  when  this  point  of  "no  draft"  is  kept  at  a  certain 
determined  distance  ahead  of  the  feed  holes  receiving  the 
finishing  heat.  If  the  draft  is  increased  or  decreased,  this 
point  will  move  from  its  proper  place  almost  immediately  the 
rate  of  progress  seems  to  be  arrested. 

William  A.  Butler,  a  ceramic  engineer,  who  has  given  some 
good  advice  to  continuous  kiln  operators,  called  attention 
to  this  point  of  "no  draft,"  several  years  ago.  He  had 
found  by  experimenting  that  if  air  was  forced  by  means 
of  a  fan,  thru  the  cooling  ware  behind  the  fires,  the  draft 
could  be  increased  and  the  point  of  "no  draft"  still  main- 
tained in  its  proper  position.  Such  a  condition  allowed  of 
a  greater  fuel  consumption  together  with  a  more  rapid 
advance  of  the  fires.  There  is  not  the  slightest  question 
about  the  soundness  of  this  idea.  The  draft  unit  is  con- 
stantly attempting  to  create  a  vacuum  in  the  kiln,  while 
nature  is  attempting  to  fill  this  vacuum  by  supplying  air 


Coal-Fired  Continuous  Kiln          163 

from  behind.  Unless  some  mechanical  assistance  is  given  to 
this  flow  of  air  in  order  to  push  it  to  its  destination  (the 
fires)  in  larger  quantities,  the  kiln  speed  will  be  governed 
by  the  speed  with  which  the  air  can  naturally  work  its  way 
thru  the  closely  set  ware. 

NOT  HARD  TO  DETERMINE  POINT  OF  "NO  DRAFT" 

Many  operators  pay  little  attention  to  this  important 
..joint  of  "no  draft,"  with  the  result  that  it  wanders  over 
A  considerable  area.  Close  observation  for  a  few  rounds 
of  the  kiln  will  determine  its  proper  location  (which  will 
vary  in  each  kiln),  and  when  it  is  once  found  it  should  be 
maintained.  Draft  gauges  are  a  valuable  aid  to  the  burner, 
but  when  not  provided,  he  can  soon  learn  to  control  the 
draft  to  a  great  extent  by  noting  with  his  hand  the  dis- 
tance above  the  feed  holes,  in  the  finishing  zone,  to  which 
the  hot  air  is  forced. 

After  the  finishing  heat  has  been  reached  in  a  section 
it  is  the  general  rule  to  maintain  the  fires  for  a  suffi- 
cient time  to  give  the  ware  a  "soaking."  This  "soaking" 
fire  is  usually  maintained  over  an  entire  section  at  least, 
the  fuel  being  fed  in  such  quantities  and  at  such  intervals 
as  will  maintain  a  fairly  constant  temperature.  The  heat 
generated  in  this  section  not  only  improves  the  ware,  but 
it  furnishes  "backing"  for  the  high  fire  section  by  increas- 
ing the  temperature  of  the  air  of  combustion.  There 
is  no  waste  of  fuel  in  this  practice  because  the  amount 
used  on  the  fires  ahead  is  decreased  in  proportion. 

UNLOADERS   SHOULD    NOT    BE   TOO    NEAR    FIRE 

Every  effort  should  be  made  to  keep  a  red  heat  in  at 
least  three  sections  behind  the  finishing  fire.  This  is  not 
difficult  if  the  unloading  section  is  kept  far  enough  be- 
hind the  fire.  Opening  sections  too  close  to  the  fire 
greatly  decreases  the  efficiency  of  the  kiln  and  results 
in  numerous  troubles.  Sometimes  the  ware  is  cooled  too 
rapidly,  resulting  in  cracked,  checked,  or  brittle  products. 

No  rule  can  be  made  regarding  the  number  of  sections 
to  be  carried  in  a  circuit,  but  roughly  it  should  be  as 
many  as  can  be  handled  and  still  get  the  proper  draft. 
It  is  useless  to  connect  more  sections  than  the  fan  or 
stack  can  handle  properly,  for  under  such  conditions  the 
capacity  is  bound  to  be  reduced. 

After  all,  the  continuous  kiln  is  a  very  simple  proposi- 


164     Clay  Plant  Construction  and  Operation 

tion.  It  is  the  clayworker  himself  who  makes  it  other- 
wise. It  is  quite  safe  to  say  that  a  well  designed  con- 
tinuous kiln  is  far  simpler  to  operate  than  a  battery  of 
down-draft  kilns,  and  requires  a  far  smaller  knowledge 
of  the  scientific  side  of  ceramics.  The  greatest  surprise 
most  successful  continuous  kiln  operators  have  had,  is 
the  discovery,  after  a  more  or  less  lengthy  period  of  dis- 
appointment and  dissatisfaction,  that  about  all  that  is 
necessary  to  make  their  kilns  work  properly,  is  an  or- 
dinary amount  of  common-sense  and  good  judgment. 


CHAPTER  XV 


Operating  a  Gas-Fired  Chamber  Kiln 

O  THE  UNINITIATED,  who  have  merely  observed  a 
producer-gas-fired  continuous  kiln  during  operation, 
it  seems  to  be  the  most  simple  and  easily  operated  kiln 
in  existence.  There  can  be  little  doubt  but  that  such  is 
the  case  when  once  the  operator  grasps  the  basic  principles 
of  operation  and  gets  thoroly  acquainted  with  his  kiln.  Until 
a  certain  degree  of  experience  has  been  reached,  however, 
especially  in  regard  to  the  handling  of  the  draft,  the  num- 
ber of  chambers  to  carry  in  the  circuit  and  the  manufacture 
of  efficient  producer  gas,  the  operator  is  very  likely  to  come 
to  the  conclusion  that  instead  of  being  the  easiest,  it  is  the 
most  difficult  of  all  kilns  to  handle.  The  fact  is,  it  is  prac- 
tically impossible  for  green,  untrained  men  to  take  hold 
of  this  kiln  and  make  a  success  of  it.  After  being  taught 
the  elementary  principles,  however,  any  man  who  will  use 
his  brains  can  become  a  successful  operator.  The  gas  kiln 
is  really  the  most  scientific  of  all  kilns  in  its  operation  and, 
this  being  the  case,  it  can  be  brought  to  a  point  where  its 
handling  becomes  almost  automatic.  This  fact  often  leads 
an  operator  into  careless  ways  with  the  result  that  a  few 
poor  chambers  will  follow  a  string  of  good  ones. 

There  is  no  question  but  that  the  gas-fired  kiln  has  a  poor 
reputation  in  some  parts  of  the  country,  even  to  the  extent 
of  being  looked  upon  as  a  failure.  There  are  many  reasons 
for  this,  but  none  of  them  have  to  do  with  the  principle  of 
using  producer  gas  in  connection  with  a  continuous  kiln. 

EARLY  TROUBLE  DUE  TO  LACK  OF  KNOWLEDGE 

Producer-gas-fired  continuous  kilns  have  been  in  use  in 
this  country  only  a  comparatively  short  time.  The  first  of 
these  were  decidedly  experimental  and  naturally  the  results 
were  not  at  all  satisfactory  to  the  clayworker.  Much  of  the 
trouble  was  due  to  a  lack  of  knowledge  concerning  the  proper 

165 


166     Clay  Plant  Construction  and  Operation 

methods  of  construction,  the  lack  of  trained  operators  and  a 
very  great  deal  to  the  old  type  of   suction  producers. 

With  the  increased  knowledge  that  has  come  in  the  past 
few  years,  the  constructional  faults  are  being  rapidly  over- 
come, trained  operators  are  now  available  and  the  newer 
types  of  gas  producers  have  made  it  possible  to  produce  a 
high  grade,  efficient  gas. 

As  in  the  case  of  the  coal-fired  continuous  kiln  there  are 
certain  "standard"  burning  rules  which  must  'be  used  as 
a  basis  for  starting  a  new  kiln,  but  as  each  kiln  develops 
its  own  peculiarities  these  rules  must  be  changed  to  meet 
the  conditions. 

Gas  kilns  probably  take  longer  to  get  into  normal  work-' 
ing  order  than  do  other  types,  altho  this  is  not  a  general  rule. 
Besides  the  heating  up  of  the  masonry  and  ground  under 
the  kiln,  which  takes  several  rounds,  there  is  the  necessity 
of  training  men  for  the  work  on  the  producers.  The  diffi- 
culty involved  in  accomplishing  this  latter  end  depends  to  a 
large  extent  on  the  fuel  .used  and  the  intelligence  of  the 
men. 

GAS    MANUFACTURE 

The  success  of  the  gas  kiln  depends  largely  upon  the  op- 
eration of  the  producers.  The  pressure  producer  is  not  ordi- 
narily difficult  to  handle,  but  this  depends  largely  on  the  kind 
of  coal  available. 

Unless  the  producers  are  especially  designed  for  the  use 
of  slack,  this  type  of  fuel  cannot  be  used.  Nut,  run-of-mine 
and  lump  coal  are  satisfactory,  the  nut  giving  the  best  re- 
sults when  it  can  be  obtained.  When  run-of-mine  or  lump 
are  used  the  large  lumps  must  be  broken  up,  while  run-of- 
mine  containing  much  slack  must  be  avoided.. 

The  principal  requirements  of  a  coal  for  producer  work 
are  that  it  be  high  in  volatile  matter  and  low  in  ash  and 
sulphur,  which  means  that  it  should  be  non-clinkering.  To 
be  high  in  volatile  matter,  however,  is  not  enough.  Many 
coals  have  a  fairly  high  volatility  but  give  it  off  with  a 
rush,  thus  flooding  the  kiln  with  gas  for  a  few  minutes,  fol- 
lowing which  the  supply  is  poor.  The  ideal  coal  is  one  that 
gives  off  its  volatile  matter  slowly,  keeping  up  a  steady 
supply  from  this  source  while  the  CO  is  coming  from  the 
fixed  carbon.  Coals  high  in  fixed  carbon  and  low  in  volatility 
can  be  used  successfully,  but  such  coals  are  consumed  slowly 
or,  in  other  words,  give  off  their  gas  slowly.  The  result 


Gas-Fired  Chamber  Kiln  167 

is  that  greater  producer  capacity  is  required  in  order  to  keep 
up  the  gas  supply. 

Clinker  is  the  greatest  enemy  of  gas  producers  and,  if 
there  is  any  possibility  whatever  of  avoiding  a  clinkering 
coal,  it  should  be  done.  If  it  is  not  possible  to  avoid  its  use, 
success  can  only  be  had  with  producers  designed  by  experts 
expressly  for  the  fuel  in  hand. 

DETERMINING  TYPE  OF  COAL  TO  USE 

There  are  a  great  number  of  ideal  producer  coals  in  dif- 
ferent parts  of  the  country  and  experiments  should  be  made 
until  the  best  one  has  been  located.  The  analysis  of  a  coal 
will  tell  very  little  about  its  adaptability,  but  it  will,  of 
course,  give  an  idea  as  to  whether  it  is  worth  trying  or  not. 
Experiments  have  shown  conclusively  that  with  two  coals 
having  very  nearly  the  same  analysis,  one  will  be  almost 
twice  as  efficient  as  the  other.  One  of  the  very  safest 
plans  to  follow  when  looking  for  a  good  producer  coal  is  to 
consult  the  manager  of  the  nearest  domestic  gas  plant.  Such 
a  plant  uses  the  highest  grades  of  gas  coal,  as  a  general 
rule,  and  information  as  to  its  source  of  supply  will  be 
valuable.  Usually,  it  will  be  a  good  investment  to  pay  from 
twenty-five  to  thirty-five  per  cent,  more  than  the  local  market 
price  in  order  to  obtain  a  high-grade  coal,  as  the  difference 
is  easily  saved  in  the  added  efficiency  of  the  gas  and  the 
lowered  cost  of  the  labor  required  to  handle  the  producers. 

Special  producers  are  designed  for  use  with  peat,  lignite, 
anthracite  and  low-grade  bituminous  coals.  In  fact,  any 
sort  of  fuel  can  be  used  in  a  gas  producer,  providing  the 
latter  is  of  the  proper  design. 

RATE  AT  WHICH  PRODUCER  SHOULD  BE  FED 

The  rate  of  feeding  coal  into  the  producer  depends  upon 
its  size  or  capacity,  and  the  fuel.  A  six-foot  producer  work- 
ing under  easy  conditions  with  a  good  coal  will  consume 
from  160  to  200  pounds  per  hour.  There  is  a  certain  height 
in  each  producer  at  which  the  top  of  the  fuel  bed  should 
be  kept.  This  is  usually  slightly  below  the  outlet  flue. 
Naturally,  fuel  cannot  be  fed  faster  than  it  is  consumed  or 
it  will  rise  above  its  proper  level,  which  is  the  gauge  that 
regulates  the  rate  of  feeding. 

Pokering  is  a  very  important  part  of  producer  operation. 
This  consists  of  dropping  a  long  poker  thru  the  poke  holes 
in  the  top  of  the  producer  and  practically  "stirring"  the  fuel 


168     Clay  Plant  Construction  and  Operation 

bed.  The  pokers  should  reach  to  the  grates  and  the  poker- 
ing should  be  done  in  such  a  way  as  to  affect  the  entire  bed 
from  top  to  bottom.  The  idea  is  to  break  up  any  clinker 
over  the  grate  that  may  prevent  the  proper  distribution  of 
the  air  blast  and  to  loosen  up  the  fuel  so  that  the  air  dis- 
tributes itself  thru  it  evenly,  thus  preventing  the  formation 
of  holes  or  channels  thrii  it.  The  amount  of  pokering  neces- 
sary depends  entirely  upon  the  kind  of  fuel  used.  Sometimes 
it  must  be  done  every  hour.  At  other  times,  every  three 
or  four  hours  is  sufficient.  The  producer  man  should  con- 
stantly watch  the  surface  of  the  fuel  bed  for  "holes"  or 
bright  spots  which  show  that  the  air  is  "channeling"  and, 
when  one  is  noted,  the  poker  should  be  used  at  once  to 
fill  it  up. 

PRESSURE  AT  BLOWER  SHOULD   BE  SIXTY  POUNDS 

The  steam  pressure  at  the  blower  should  be  kept  at  sixty 
pounds  when  the  producer  is  operating  normally.  It  is  quite 
important  that  the  pressure  be  kept  constant  under  ordinary 
conditions  and  that  it  be  not  allowed  to  fluctuate  with  the 
boiler  pressure.  The  only  safe  method  of  handling  this  prob- 
lem is  to  install  a  regulating  valve  in  the  steam  line  between 
the  boiler  and  the  blowers.  This  will  insure  constant 
pressure. 

The  air  blast  from  the  blower  should  indicate  from  \l/2 
to  2  inches  of  water  on  a  U-tube  for  best  results,  altho  when 
an  increased  volume  of  gas  is  required  it  is  necessary  to 
run  it  higher. 

The  gas  pressure  in  the  producer  necks  should  register 
about  34-inch  on  the  U-tube.  Maintaining  a  much  greater 
pressure  than  this  is  likely  to  result  in  the  gas  forcing  its 
way  out  of  the  gas  flues  at  every  crack  on  its  way  from  pro- 
ducers to  kiln.  When  this  pressure  drops  close  to  the  zero 
mark  a  dangerous  condition  exists,  especially  if  the  gas  is 
hot.  Good  producer  gas  is  highly  explosive  when  at  certain 
temperatures  and  when  mixed  with  air.  As  long  as  a 
pressure  is  kept  on  the  gas,  no  air  can  be  drawn  into  the 
flues.  But  when  there  is  no  pressure  and  the  kiln  is  creating 
a  suction,  air  may  be  drawn  into  the  flues,  and  if  the  condi- 
tions are  right,  a  serious  explosion  will  result.  Several  kilns 
have  been  badly  damaged  thru  explosions  caused  by  such 
conditions. 

GAS    TEMPERATURE    EXCEEDINGLY    IMPORTANT 

The  temperature  of  the  gas  as  it  leaves  the  producers  is 


Gas-Fired  Chamber  Kiln  169 

most  important.  One  of  the  greatest  troubles  producer  gas 
users  have  hacl  in  the  past  is  due  to  the  fact  that  the  gas 
"cracks"  at  certain  temperatures  and  rapidly  deposits  either 
soot  or'  tar  in  the  gas  conveyors  or  flues.  This  soot  and  tar 
chokes  the  flues  and  shuts  off  the  supply  at  the  burners,  thus 
necessitating  frequent  "burn-outs,"  as  the  process  of  lighting 
up  and  burning  out  the  deposit  is  called.  The  time  con- 
sumed by  these  "burn-outs"  is  a  dead  loss,  since  the  kiln  has 
to  be  shut  down  during  that  period,  which  covers  from 
twelve  to  twenty-four  hours. 

The  conditions  under  which  gas  "cracks"  are  fairly  definite- 
ly known  and  there  is  really  no  good  reason  why  there  should 
be  so  much  trouble  from  this  source.  Of  course,  producers 
are  designed  which  overcome  the  trouble,  or  scrubbers  could 
be  installed  for  the  same  purpose  but,  as  only  the  simple 
forms  of  producer  are  used  on  clay  plants,  and  since  scrub- 
bers are  expensive  and  unnecessary,  the  only  method  left  to 
the  clayworker  is  temperature  control. 

Producer  gas  made  in  the  type  of  producer  generally  used 
will  deposit  tar  at  temperatures  below  800  degrees  Fahr.  and 
will  deposit  soot  at  temperatures  above  900  degrees  Fahr. 
These  temperatures  refer  to  the  gas  as  it  leaves  the  pro- 
ducers. 

It  will  be  seen  that  there  is  a  neutral  zone  between  800 
degrees  and  900  degrees  Fahr.  and,  when  the  gas  is  kept 
within  this  zone,  the  minimum  amount  of  tar  and  soot  will 
be  deposited. 

EVERY     COAL     HAS     NO-DEPOSIT     TEMPERATURE 

Experiments  made  by  the  author  seem  to  show  that  each 
coal  has  a  definite  temperature  at  which  there  is  practically 
no  deposit,  altho  all  the  coals  experimented  with  remained 
within  the  above  mentioned  range.  By  closely  watching 
pyrometers  installed  in  the  gas  necks  it  has  been  possible  to 
operate  a  kiln  for  fifty-nine  days  before  being  troubled  with 
choked  flues ;  and  by  the  simple  method  of  keeping  the  gas  at 
the  proper  color,  it  was  possible  to  run  without  interruption 
for  from  thirty  to  forty  days.  When  it  is  taken  into  con- 
sideration that  the  average  gas  kiln  requires  burning  out 
every  seven  to  ten  days  it  will  be  seen  how  important  it  is 
to  watch  the  gas  temperature. 

It  is  much  better  to  keep  the  gas  too  cool  than  too  hot. 
Tar  is  troublesome  at  the  valves,  but  it  takes  up  very  little 


170     Clay  Plant  Construction  and  Operation 

space  in  the  flues  and  accumulates  slowly.  On  the  other 
hand,  soot  accumulates  very  rapidly  and  soon  causes  trouble. 
It  should  also  be  borne  in  mind  that  a  high  producer  tem- 
perature means  a  reduction  in  the  quantity  of  gas,  for  it  is 
the  burning  of  the  gas,  or  the  ingredients  which  make  up 
the  gas,  that  produces  the  high  temperature. 

When  the  gas  temperature  is  between  800  and  900  degrees 
Fahr.  the  gas  has  a  rich  yellow  color,  tinged  with  light  green, 
and  if  it  is  held  at  this  color  it  cannot  be  far  from  its  most 
efficient  state.  Hot  gas  is  nearly  colorless  except  that  some 
smoke  is  seen  in  it.  When  it  is  very  hot,  it  appears  as  nearly 
all  smoke.  Such  gas  is  almost  worthless  except  for  its  sen- 
sible heat. 

When  gas  is  at  its  best  it  will  not  ignite  at  the  poke  holes 
when  a  match  is  applied  to  it.  As  the  temperature  increases 
however,  it  will  ignite  readily  and  will  finally  reach  a  stage 
where  it  will  issue  as  flame  instead  of  gas. 

HOW    TO    CLEAN    A    PRODUCER 

There  are  various  methods  of  cleaning  the  producers.  On 
some  plants  the  clinker  is  removed  each  day;  on  others,  only 
once  each  week.  A  great  deal  depends  upon  the  amount  of 
clinker  or  ash  the  coal  produces,  but  in  any  case  it  is  quite 
unnecessary  to  clean  as  often  as  every  day.  Cleaning,  espe- 
cially in  hot  weather,  is  a  nasty  job  and  as  much  of  it  as 
possible  should  be  avoided.  In  some  cases  all  of  the  clinker 
is  pulled  out  from  beneath  the  producers  thru  the  water 
pans,  but  it  is  far  easier  and  quicker  to  remove  all  possible 
thru  the  clean-out  doors  and  then  with  a  bar  punch  the 
remaining  clinker  to  the  bottom  where  it  is  then  pulled  out 
thru  the  pans.  Two  rows  of  sight  holes  are  provided  on 
most  producers.  Sufficient  clinker  should  be  removed  so 
that  the  fire  may  be  seen  thru  the  lower  row  and,  when  the 
clinker  bed  grows  sufficiently  thick  to  cover  the  upper  row, 
it  is  time  to  clean  again. 

When  producers  are  started  it  is  best  to  dump  in  enough 
ashes  to  cover  the  grates.  A  wood  fire  is  then  started  and 
coal  fed  as  rapidly  as  it  will  ignite,  until  the  proper  fuel  bed 
level  is  reached.  The  blowers  are  then  started  and  run 
for  a  few  hours  until  the  gas  begins  to  have  the  proper  ap- 
pearance. During  this  time  the  products  of  combustion  are 
let  out  thru  the  clean-out  doors  in  the  gas  necks. 

When  feeding  gas  to  a  kiln  which  is  just  being  started 
it  is  always  best  to  have  the  gas  quite  hot,  that  is,  from 


Gas-Fired  Chamber  Kiln  171 

1,100  to  1,200  degrees  Fahr.  Such  gas  will  ignite  readily, 
while  cool,  rich  gas  may  cause  an  explosion,  with  serious 
consequences.  It  is  never  safe  to  attempt  to  light  gas  in 
a  continuous  kiln  chamber  unless  red  heat  can  be  plainly 
seen.  This  can  be  done  by  one  who  has  become  expert  in 
the  handling  of  gas,  but  even  under  such  circumstances,  kilns 
have  been  badly  damaged  by  explosions,  the  cause  of  which 
were  unknown. 

METHOD   TO    FOLLOW    IN    BURNING    OUT    FLUES 

Burning  out  the  deposit  in  the  flues  is  a  comparatively 
simple  matter.  The  kilns  of  latest  design  are  equipped  with 
flues  which  connect  the  fan  with  the  gas  flues.  The  older 
kilns  have  stacks,  called  "burn-out"  stacks,  which  provide 
draft  for  the  same  purpose.  When  the  stacks  are  used  the 
process  is  a  slow  one,  consuming  considerable  time.  When 
the  flues  can  be  connected  with  the  fan,  the  soot  and  tar 
are  consumed  very  quickly.  To  start  the  deposit  burning  it 
is  only  necessary  to  open  the  wicket  in  the  main  gas  flue 
near  the  producers  and  start  the  draft.7  The  temperature  in 
the  flues  is  sufficient  to/  ignite  the  soot  and  tar.  In  order 
to  burn  out  the  distributing  flues,  the  gas  valves  on  the 
chambers  that  are  still  red  are  opened  slightly  as  is  also 
one  or  two  of  the  gas  ports.  This  pulls  the  heat  from  the 
chambers  thru  the  distributing  flues  and  burns  the  deposit. 
Care  must  be  taken  not  to  let  the  temperature  in  these  flues 
become  too  high  or  the  iron  gas  valves  will  be  damaged. 
Simply  closing  the  main  gas  valve  stops  the  fire  in  these 
flues.  If  they  are  not  burned  clean  at  the  first  attempt,  they 
should  be  allowed  to  cool  somewhat  and  the  operation  then 
repeated.  Of  course,  only  those  distributing  flues  on  cham- 
bers which  are  at  red  heat  can  be  burned  out  in  this  way, 
but  as  a  different  set  of  chambers  are  in  this  condition  at 
each  burn-out  period,  they  all  receive  attention  in  time.  The 
distributing  flues  do  not  accumulate  much  of  a  deposit  as 
they  are  in  use  for  only  a  short  period  at  a  time,  and  at 
that  time  are  at  a  fairly  high  temperature  on  account  of  their 
proximity  to  the  heated  chambers  on  each  side. 

It  is  very  easy  to  determine  when  the  flues  have  been 
burned  clean.  While  the  deposit  is  burning  a  thick  smoke 
issues  from  the  fan  stack.  When  this  ceases  the  flues  can 
be  assumed  to  be  clean. 

SETTING 

There    is    nothing    complicated    about    the    setting    in    a 


172     Clay  Plant  Construction  and  Operation 

chamber  kiln  as  each  chamber  is  exactly  like  a  rectangular 
down-draft.  Any  method  of  setting  which  is  used  in  a 
down-draft  kiln  can  be  followed  successfully.  This  applies 
to  brick,  hollow-ware  or  other  ware.  In  the  one  side  fire 
type  there  is  sometimes  a  tendency  on  the  part  of  the  gas 
to  pull  to  the  side  of  the  chamber  opposite  the  flash  wall,  but 
more  often  the  tendency  is  to  short  cut  to  the  floor  close 
to  the  flash  wall.  In  the  former  case  it  is  necessary  to 
tighten  the  setting  against  the  partition  wall  and  open  it 
somewhat  toward  the  flash  wall,  while  in  the  latter  case  the 
method  is  reversed  and  the  setting  made  tight  against  the 
flash  wall. 

In  most  gas  kilns  it  has  been  found  best  to  allow  plenty  of 
room  between  setting  and  crown  if  speed  is  desired.  Ex- 
periments will  have  to  be  made  with  each  kiln  to  find  out  at 
what  height  the  greatest  kiln  speed  can  be  attained.  Experi- 
ments carried  on  by  the  author  seem  to  show  that  after 
passing  a  certain  height  it  becomes  difficult  to  reach  the  bot- 
toms which,  of  course,  slows  the  kiln  on  account  of  the 
extra  time  consumed  in  getting  the  bottom  ware  to  the  fin- 
ishing point.  On  the  other  hand,  it  was  found  that  to  set 
below  a  certain  level  did  not  increase  the  kiln  speed  at  all, 
taking  about  the  same  amount  of  time  to  finish  the  chamber 
properly.  Naturally,  the  material  used  and  the  ware  pro- 
duced has  a  great  deal  to  do  with  the  results.  When  the 
raw  material  has  a  very  wide  burning  range  and  there  can 
be  a  wide  difference  between  the  temperature,  top  and  bot- 
tom, without  injury  to  the  top,  the  ware  can  be  set  higher 
without  decreasing  the  speed.  Also  when  fairly  soft  ware 
can  be  disposed  of,  there  is  not  the  necessity  of  spending  so 
much  time  in  getting  the  bottom  to  somewhere  near  the 
same  temperature  as  the  tops. 

WATERSMOKING 

Chamber  kilns  are  equipped  with  watersmoking  flues  and, 
on  account  of  their  down-draft  design,  watersmoking  can 
be  efficiently  done.  The  chamber  from  which  the  heated  air 
is  to  be  drawn  should  be  selected,  not  on  account  of  its  loca- 
tion behind  the  fire,  but  on  account  of  its  temperature.  Gen- 
erally, the  connection  to  the  watersmoking  flue  is  made  with 
the  chamber  ahead  of  the  last  one  broken  into.  The  heat 
from  this  is  drawn  into  the  chamber  to  be  watersmoked  until 
the  temperature  of  the  latter  is  as  high  as  it  is  possible  to 
get  it.  The  connection  with  the  warm  chamber  is  then 


Gas-Fired  Chamber  Kiln 


173 


broken  and  advanced  to  the  chamber  ahead,  the  temperature 
of  which,  of  course,  is  higher.  The  heat  from  this  chamber 
brings  the  temperature  of  the  watersmoker  still  higher  and, 
as  a  rule,  is  sufficient  to  finish  this  period.  This  practice 
is  hardly  necessary  except  in  cases  of  clays  which  scum 


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easily.  When  efflorescence  is  not  feared  it  is  the  usual  prac- 
tice to  get  what  heat  is  possible  from  one  chamber  and  then 
connect  the  watersmoker  to  the  main  burning  circuit. 

The  watersmoker  is  isolated  by  means  of  paper  partitions 
over  its  own  bag  wall  openings  and  those  of  the  chamber 
ahead,  which  is  being  set.  Great  care  should  be  taken  to 
have  these  partitions  properly  pasted  on  or  draft  troubles 
are  sure  to  occur.  When  all  of  the  connections  are  made 
with  the  watersmoking  flue,  the  connection  between  the 


174     Clay  Plant  Construction  and  Operation 

chamber  to  be  watersmoked  and  main  draft  flue  is  made. 
This  does  not  in  any  way  interfere  with  the  draft  or  opera- 
tion of  the  burning  section.  The  watersmoker  is  as  inde- 
pendent as  if  it  were  a  single  down-draft  kiln. 

When  the  watersmoking  is  completed  a  hook  is  inserted 
thru  the  sight  holes  at  each  end  of  the  chamber  and  the 
paper  partitions  torn.  The  draft  is  then  "split,"  part  of  it 
being  taken  thru  the  watersmoker  and  part  thru  the  chambti 
behind.  This  is  accomplished  by  allowing  both  connections 
with  the  main  draft  flue  to  remain  and  partially  closing  the 
dampers  on  each  one.  The  effect  of  this  is  to  reduce  the 
shock  of  the  hot  gases  from  the  burning  section  on  the  water- 
smoked  ware.  As  the  temperature  in  the  new  unit  increases, 
its  damper  is  opened  wider  while  the  one  behind  is  closed 
to  the  same  extent.  This  is  carried  on  until  all  of  the  draft 
is  being  taken  thru  the  new  unit,  at  which  time  the  connec- 
tion with  the  chamber  behind  is  broken.  This  process  of 
connecting  up  a  new  unit  will  take  from  four  to  twelve  hours 
according  to  the  raw  material.  Fig.  74  shows  a  diagram  of 
this  process. 

It  is  only  necessary  to  tear  the  paper  partitions  at  each 
end  of  a  chamber  as  the  draft  will  then  tear  off  the  balance 
at  once. 

Starting  a  gas  kiln  is  not  a  difficult  matter.  As  soon  as 
two  or  three  chambers  of  ware  have  been  set,  about  half 
of  the  floor  openings  in  the  chamber  directly  behind  should 
be  covered  with  brick.  The  wickets  of  this  chamber  should 
then  be  put  up  and  mudded  over.  In  the  chamber  behind 
this  empty  chamber,  or  the  second  behind  the  first  chamber 
set,  a  few  of  the  floor  tile  should  be  taken  up  so  that  fires 
may  be  started  directly  beneath  the  bags  of  the  chamber 
ahead.  Fires  are  then  started  beneath  these  bags  with 
wood  and  coal,  preferably  slack.  Connection  is  then  made 
between  the  main  draft  flue  and  the  last  chamber  set  as 
shown  in  Fig.  75. 

The  fires  are  kept  up  until  the  bag-walls  of  the  empty 
chamber  and  the  crown  just  above  are  at  a  red  heat,  when 
the  gas  is  turned  into  it.  Burning  gas  in  the  empty  chamber 
soon  brings  the  walls  and  floor  to  a  red  heat  and  naturally 
very  soon  heats  up  the  bag-walls  of  the  chamber  ahead,  which 
is  full  of  ware. 

Considerable  care  is  necessary  during  this  period.  The 
air  control  for  the  gas  burning  in  the  empty  chamber,  and 


Gas-Fired  Chamber  Kiln  175 

later,  in  the  chambers  ahead,  is  thru  the  coal  fires  which  are 
still  kept  burning  in  the  under-flues.  If  these  fires  are  al- 
lowed to  get  too  low  or  are  kept  too  open  so  that  too  much 
cold  air  is  admitted  to  the  gas,  the  flame  will  go  out  and 
the  conditions  may  be  right  for  an  explosion.  It  is  very  easy 
to  tell  by  the  appearance  of  the  gas  when  conditions  are  not 
right.  It  will  burn  brightly  when  the  air  control  is  right  and 
become  dark  and  smoky  when  it  is  wrong.  It  should  be  re- 
membered too,  that  these  coal  fires  must  furnish  the  pre- 
heated air  necessary  for  proper  combustion  until  several 
chambers  of  ware  have  been  finished.  To  let  the  fires  out 
after  the  first  chamber  had  been  finished  would  mean  that 
this  chamber  would  lose  its  heat  at  once  and  this  would 
prevent  the  proper  finishing  of  the  next  chamber  of  ware.  It 
is  the  best  practice  to  wait  until  the  fourth  full  chamber  is 
ready  to  light  before  allowing  the  coal  fires  to  die  out. 

The  principal  reasons  for  having  an  empty  chamber  be- 
tween the  coal  fires  and  the  first  full  chamber  are,  that  the 
heat  becomes  somewhat  tempered  in  passing  thru  the  empty 
chamber  and,  therefore,  does  not  shock  the  ware,  and  that 
it  is  much  easier  to  keep  the  gas  lit  in  the  empty  chamber 
than  it  would  be  in  a  full  chamber,  on  account  of  the  bulk 
of  ware  it  is  necessary  to  heat  up  before  a  dull  red  color  is 
reached  around  the  bags. 

BURNING 

As  a  rule  gas  is  kept  only  on  the  high  fire  chamber,  altho 
sometimes  it  is  lit  in  the  one  ahead  of  the  high  fire  chamber 
before  the  latter  is  finished.  Very  seldom  is  the  gas  kept  on 
a  chamber  after  it  is  finished  for,  in  a  properly  operated 
kiln,  it  is  absolutely  unnecessary. 

The  conditions  in  a  chamber  when  it  is  ready  for  the  gas 
vary,  of  course,  with  the  raw  material,  kind  of  ware  and 
the  kiln  operation.  When  a  chamber  finishes  at  around  2,000 
degrees  Fahr.  the  chamber  ahead  will  have  a  temperature  of 
from  1,100  to  1,500  degrees  Fahr.  It  is  only  necessary  to 
open  the  valve  connecting  the  main  gas  flue  with  the  dis- 
tributing flue  and  then  the  valves  in  the  "down  takes"  lead- 
ing to  the  gas  ports.  As  soon  as  these  valves  are  opened 
the  gas  ignites  and  the  chamber  is  under  fire.  The  main 
valve  on  the  finished  chamber  is  then  closed. 

In  the  gas  kiln  the  center  of  the  chamber  has  a  great 
tendency  to  get  ahead  of  the  ends.  It  is  possible  to  correct 
this  by  cutting  down  the  gas  supply  at  the  middle  ports,  but 


176     Clay  Plant  Construction  and  Operation 

this  naturally  slows  up  the  burning.  The  best  method  of 
overcoming  this  difficulty  and,  at  the  same  time  maintaining 
or  even  increasing  the  burning  speed,  is  to  light  up  the  two 
ports  in  each  end  of  the  chamber  several  hours  before  the 
high  fire  chamber  is  finished.  This  gives  the  ends  a  start 
over  the  center  which  will  not  be  more  than  equalized  until 
the  chamber  is  about  finished,  even  with  the  center  ports 
going  at  top  pressure. 

"LEAD  AHEAD"  GAS  TO   INCREASE   CAPACITY 

When  the  kiln  cannot  be  kept  up  to  the  capacity  of  the 
factory  with  only  a  single  chamber  on  fire  at  a  time,  as  is 
sometimes  the  case,  the  gas  is  often  "led  ahead."  In  this  case 
the  gas  is  lit  in  the  chamber  ahead  of  the  high  fire  chamber, 
from  six  to  twelve  hours  before  the  latter  is  finished.  In 
other  words,  gas  is  kept  on  two  chambers.  In  this  way  the 
chamber  ahead  of  the  high  fire  not  only  gets  the  waste  heat 
from  the  high  fire  chamber,  but  also  the  heat  from  its  own 
fires.  In  this  way  the  burning  speed  can  be  materially  in- 
creased. Of  course,  this  can  only  be  done  when  there  is 
sufficient  producer  capacity  to  supply  both  chambers. 

Perfect  control  can  be  had  in  a  gas  kiln  thru  the  proper 
handling  of  the  valves.  There  is  not  the  slightest  excuse  for 
a  fluctuation  in  the  temperature -of  a  chamber  from  one  end 
to  the  other.  The  sight  holes  above  the  bags  at  each  end 
of  the  chambers  provide  a  means  of  detecting  any  variations 
in  temperature  almost  instantly  and  the  manipulation  of  the 
valve  cords  provides  easy  correction. 

It  is  always  necessary  for  the  operator  to  give  unceasing 
attention  to  the  valves.  Tar  and  soot  are  constantly  accumu- 
lating between  the  valves  and  their  seats,  and  the  gas  flow 
is  thus  diminished.  This  is  especially  true  when  the  valves 
are  only  "cracked,"  as  the  slight  opening  is  easily  choked 
up.  Sometimes  only  one  or  two  of  the  valves  "tar  up"  and 
the  gas  that  cannot  flow  thru  them  is  forced  thru  the  other 
valves.  This  will  cause  local  hot  and  cool  spots  in  front 
of  the  affected  ports.  When  valves  choke  it  is  only  neces- 
sary to  shake  them  slightly  by  pulling  the  cords  to  clear 
them. 

NINE    CHAMBERS    FAIR    AVERAGE   TO   CARRY 

The  number  of  chambers  to  be  carried  in  a  circuit  varies 
with  the  size  of  the  fan  unit,  the  setting  and  the  condition 
of  the  kiln.  A  fair  average  would  be  nine  chambers.  One 
of  these  would  be  on  high  fire,  three  ahead  would  be  pre- 


Gas-Fired  Chamber  Kiln  177 

heating  with  the  waste  gases  from  the  fire,  while  the  fourth 
ahead  would  be  watersmoking.  Three  chambers  behind  the 
fire  would  be  preheating  the  air  for  combustion,  and  the 
fourth  behind  would  be  supplying  hot  air  for  the  chamber 
being  watersmoked.  The  fifth  behind  the  fire  would  be 
opened  so  as  to  admit  the  air  to  be  preheated  for  combustion. 
The  above  might  be  varied  by  increasing  the  number  of 
chambers  ahead  of  and  behind  the.  fires,  but  it  would  be  bad 
practice  to  carry  less  than  three  ahead  and  three  behind, 
exclusive  of  the  watersmoker  and  the  chamber  supplying 
the  watersmoker  with  heat.  See  Fig.  76. 

To  a  great  extent  the  number  of  chambers  aTiead  of  the 
high  fire  should  be  regulated  by  the  temperature  of  the  waste 
gases  as  they  are  exhausted  to  the  draft  flue.  On  some  kilns 
that  are  giving  splendid  results  the  temperature  of  the  ex- 
haust gases  is  seldom  allowed  to  get  above  80  or  100  degrees 
Fahr. 

THE   QUESTION   OF   DRAFT 

It  is  extremely  hard  to  say  just  how  much  draft  should  be 
carried  on  a  gas  kiln.  Each  kiln  will  vary  somewhat  ac- 
cording to  the  construction.  Some  kilns  are  so  poorly  built 
that  it  is  impossible  to  get  sufficient  draft  to  insure  a  high 
burning  speed,  on  account  of  the  great  number  of  air  leaks 
between  the  fan  and  the  fire.  Up  to  a  certain  point  the 
higher  the  draft  used  the  greater  the  burning  speed  will  be. 

Under  normal  conditions  a  kiln  which  finishes  a  chamber 
every  twenty-four  to  thirty-six  hours  should  have  one  and 
one-half  inches  of  draft  on  the  chamber  ahead  of  the  high 
fire  chamber,  and  two  inches  on  the  second  chamber  ahead 
of  the  high  fire.  These  draft  readings  refer  to  conditions 
just  after  a  fresh  chamber  has  been  lighted  up.  Normally, 
the  draft  will  show  a  reduction  of  approximately  one-half 
inch  between  the  time  a  chamber  is  lighted  up  and  finished. 
This  means  that  on  the  chamber  which  has  a  two-inch  read- 
ing when  a  fresh  chamber  is  lighted,  the  reading  will  be  one 
and  one-half  inches  when  the  chamber  is  finished. 

It  is  generally  impossible  to  run  around  a  big  kiln  with 
a  "set"  draft  reading,  as  the  amount  of  draft  necessary  is 
bound  to  vary  in  different  chambers  for  several  reasons, 
principally  constructional.  An  expert  burner,  in  addition  to 
using  his  draft  gauges,  is  governed  by  the  sharpness  of  the 
flame  as  it  leaves  the  ports.  Under  high  draft  the  flame  cuts 
sharply  a^vay  from  the  ports,  while  under  low  draft  it  rolls 


178     Clay  Plant  Construction  and  Operation 


slowly  under  the  crown.  A  record  should  be  kept  on  each 
chamber  and,  as  soon  as  the  best  draft  has  been  determined, 
it  should  be  adhered  to  as  closely  as  possible  when  that 
particular  chamber  is  reached  in  the  circuit. 

FLASHED  WARE   EASILY  OBTAINED   IN   GAS   KILN 

In  ordinary  burning  the  gas  kiln  will  always  produce  oxi- 
dizing conditions,  but  reducing  conditions  can  be  easily 
obtained.  It  is  extremely  simple  to  get  flashed  ware  if  such 
is  wanted,  altho  this  result  will  not  occur  accidentally. 
However,  as  is  the  case  with  all  continuous  kilns,  it  is  very 


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hard  to  get  any  quantity  of  blacks  or  very  dark  colors.  This 
is  due  to  the  fact  that,  while  these  colors  can  be  easily  given 
to  the  ware  when  it  is  under  fire,  as  soon  as  it  is  off  fire  the 
ware  is  reoxidized  by  passing  over  it  the  air  necessary  for 
combustion  in  the  chambers  ahead.  Under  the  continuous 
system  it  is  impossible  to  avoid  this.  Some  clays  do  not 
easily  lose  the  flash  and,  of  course,  in  such  cases,  the  dark 
colors  are  obtainable.  Ordinarily,  the  colors  predominating 
where  flashed  ware  is  made,  are  browns,  purples,  dark  reds 
and  combination  of  these  colors. 

The  method  of  flashing  is  extremely  simple.  When  the 
finishing  point  of  the  ware  is  approached,  the  draft  is  cut 
very  low.  This  causes  the  gas  to  smoke  and  the  chamber 
is  quickly  filled.  The  chamber  is  allowed  to  remain  in  this 
condition  for  from  fifteen  to  forty-five  minutes  and  the 
draft  is  then  raised  and  the  chamber  cleaned  of  smoke. 
The  smoking  is  repeated  with  intervals  of  fifteen  to  thirty 
minutes  and  continued  until  the  required  colors  are  got- 
ten from  top  to  bottom.  Some  experimenting  is  neces- 
sary to  determine  just  how  long  it  is  necessary  to  continue 


Gas-Fired  Chamber  Kiln 


179 


the  smoking  periods.  Some  clays  take  the  required  color  in 
one  period  of  forty-five  minutes  while  others  require  the 
process  to  be  kept  up  for  ten  or  twelve  hours. 

Care  must  be  taken  during  the  reducing  periods  or  the  top 


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course  will  get  too  hot  and  be  deformed  or  melted.  It  is 
for  this  reason  that  the  chamber  is  cleared  occasionally. 
The  draft  being  increased  carries  the  heat  from  the  top  to 


180     Clay  Plant  Construction  and  Operation 

the   bottom   and   evens   up   the   temperature   of   the   chamber 
preparatory  to  another  reducing  period. 

It  must  be  remembered,  when  attempting  to  get  flashed 
ware,  that  the  conditions  in  a  gas  kiln  differ  from  those 
occurring  in  other  types.  In  order  to  get  the  chambers  off 
quickly  and  preserve  normal  conditions  ahead  and  behind, 
it  is  necessary  to  carry  the  chambers  along  to  almost  the 
finishing  point  under  normal  conditions,  leaving  the  reducing 
periods  to  a  few  hours  near  the  finish.  Also,  it  must  be 
borne  in  mind  that  the  entire  firing  period  is  only  about 
twenty-four  hours  instead  of  from  five  to  ten  days  as  is 
the  case  in  a  down-draft  kiln  or  from  three  to  four  days 
in  a  coal-fired  continuous.  With  clays  that  are  likely  to 
"black  core,"  any  attempt  to  reduce  a  chamber  over  the 
entire  firing  period  will  cause  trouble,  thru  the  effects  on 
the  ware  in  the  chambers  ahead.  This  ware  is  passing  thru 
the  oxidation  period  while  the  chamber  on  fire  is  being 
"brought  up"  and,  as  all  the  gases  from  the  firing  chamber 
pass  thru  the  chambers  ahead,  it  is  absolutely  necessary  that 
these  gases  be  oxidizing  and  not  reducing. 

SUCCESS  DEPENDS  LARGELY  UPON  BACKING  HEAT 

As  in  all  other  types  of  continuous  kilns  a  great  deal  01 
the  success  of  the  gas  kiln  depends  on  keeping  the  propei 
amount  of  "backing  heat"  or,  in  other  words,  maintaining 
the  proper  temperature  in  the  chambers  behind  the  fire. 
Emptying  chambers  too  close  up  to  the  fire  always  causes 
trouble  and  lowers  the  efficiency  of  the  kiln.  Generally 
speaking,  at  least  four  closed  chambers  should  be  kept  be- 
hind the  chamber  on  fire,  the  air  being  admitted  at  the  fifth. 
Another  working  rule  is  to  keep  enough  chambers  behind 
the  fire  so  that  the  chamber  which  was  last  taken  off  fire 
does  not  lose  more  than  half  its  temperature  in  the  first 
twenty-four  hours.  Thus,  if  a  chamber  is  finished  at  2,000 
degrees,  twenty-four  hours  after  it  is  taken  off  its  tempera- 
ture should  not  be  less  than  1,000  degrees.  A  kiln  should 
always  give  good  results  if  such  a  condition  is  maintained 

FIFTEEN    CHAMBERS    BEST 

The  question  as  to  how  many  chambers  it  is  absolutely 
necessary  to  have  in  order  to  get  good  results  is  an  important 
one.  Some  kilns  have  been  condemned  as  failures  when 
the  trouble  was  entirely  due  to  the  fact  that  there  were  too 
few  chambers  to  maintain  continuous  operations.  When  a 


Gas-Fired  Chamber  Kiln  181 

chamber  holds  a  day's  run  and  can  be  burned  off  in  twenty- 
four  hours  the  kilns  should  not  have  less  than  thirteen 
chambers.  This  allows  for  ten  in  the  burning  circuit,  one 
setting  and  two  being  emptied.  Such  a  kiln  allows  prac- 
tically no  leeway  and,  to  be  operated  without  interfering 
with  the  factory,  it  must  run  like  clockwork.  Sundays, 
holidays  and  factory  delays  would  have  to  be  taken  full 
advantage  of  in  operating  such  a  kiln. 

It   is   really  best  to   provide  at  least   fifteen  chambers   for 
good  working  conditions  and  to  guard  against  emergencies. 


CHAPTER  XVI 

Suggestions  on  Plant  Location 
and    Design 


T  T  WOULD  BE  IMPOSSIBLE  in  a  single  chapter  or  even 
several  chapters,  to  attempt  to  cover  the  subject  thoroly 
of  locating  and  designing  a  clay  products  plant.  Each  pro- 
posed plant  should  be  handled  as  a  separate  engineering 
problem  as  conditions  will  vary  greatly  according  to  the 
ware  to  be  made,  the  raw  material  used  and  the  plant  loca- 
tion. 

This  chapter  will  therefore  treat  only  with  the  general 
principles  governing  the  designing  of  all  plants  no  matter 
what  the  type  of  ware  produced. 

It  is  presumed  that  in  selecting  a  plant  site  the  proper 
amount  of  consideration  has  been  given  to  such  important 
items  as  drainage,  water  supply,  railroads,  markets  and 
freight  rates. 

Speaking  of  the  industry  at  large,  there  are  too  many  in- 
stances of  lack  of  consideration  on  the  future  of  the  plant. 
This  is  often  shown  in  purchasing  the  plant  site  proper. 
Only  sufficient  land  or  suitable  land  is  acquired  to  build 
the  original  unit  and  consequently  when  the  time  for  expan- 
sion arrives  the  company  is  in  a  quandary. 

Every  successful  plant  will  grow  and  in  acquiring  a  site, 
provision  should  be  made  for  this  growth.  Land  in  the  vicin- 
ity of  a  plant  seldom  depreciates  and  generally  enhances 
in  value  so  that  even  if  too  much  is  bought  originally  it 
can  later  be  disposed  of  at  a  profit,  if  necessary. 

WARE    TO    BE    PRODUCED 

This  subject  is  generally  given  very  early  consideration, 
in  fact,  the  product  to  be  made  is  often  decided  upon  before 
the  deposit  is  located.  There  are  two  ways  of  approaching 

182 


Suggestions  on  Location  and  Design  183 

this  subject — one  to  determine  first  the  ware  to  be  made 
and  then  to  seek  a  suitable  deposit  of  raw  material  and  the 
other  to  determine  by  thoro  tests  what  types  of  ware  can 
be  produced  from  the  deposit  after  it  is  located. 

Too  often  this  most  important  item  is  approached  in  the 
wrong  way.  Either  the  product  is  determined  upon  with- 
out consideration  being  given  to  the  raw  material  available 
or  the  raw  material  is  determined  upon  without  due  con- 
sideration being  given  to  the  product  it  is  intended  to  manu- 
facture. Many  plants  have  commenced  operations  before  it 
has  been  discovered  that  the  deposit  is  not  suitable  and  in 
very  many  cases  it  has  been  the  death  knell  of  the  plant, 
so  far  as  its  original  owners  were  concerned  at  least. 

CAPACITY   OR  OUTPUT 

The  original  capacity  of  a  plant  is  usually  governed  by 
the  dryers  or  kilns.  In  considering  the  question  of  capac- 
ity of  a  new  plant  it  is  by  far  the  wisest  plan  to  figure  un- 
der rather  than  over.  If  more  ware  can  be  produced  than 
can  be  disposed  of,  part  of  the  investment  must  stand  idle, 
whereas,  if  the  reverse  is  true  it  is  always  easy  to  make  ad- 
ditions. Most  plants,  as  originally  designed,  are  poorly  bal- 
anced, one  or  the  other  of  the  departments  being  unable  to 
produce  what  the  others  can  take  care  of. 

Great  care  should  be  exercised  in  working  out  and  bal- 
ancing the  various  departments,  this  being  especially  true 
of  the  dryer  and  kiln  departments. 

Machine  equipment  whose  capacity  is  considerably  in 
excess  of  that  required  is  not  generally  economical  to 
operate.  It  is  not  good  practice  to  put  in  a  brick  machine 
having  100,000  capacity  per  day  if  only  50,000  are  to  be 
made,  with  the  idea  of  future  development.  It  is  far  more 
sensible  to  put  in  a  60,000  capacity  machine  and  when  the 
increased  demand  comes  install  an  additional  unit.  The 
large  unit  will  produce  the  best  product  when  operating 
at  its  normal  capacity  and  would  therefore  produce  the  50,- 
000  required  in  half  a  day,  leaving  a  problem  of  disposing 
of  its  crew  for  the  balance  of  the  day.  In  addition  to  this, 
a  power  plant  sufficient  to  operate  the  large  unit  Would 
be  required  and  every  machine  from  pan  to  pugmill  would 
have  to  have  the  maximum  ral.ng  or  a  great  loss  of  efficiency 
would  occur. 

Dryers   are    very    likely    to   be    under  the   desired   capacity 


184     Clay  Plant  Construction  and  Operation 

and  it  is  always  wise  to  allow  considerable  leeway  in  this 
department,  especially  as  the  depreciation  is  very  low.  It 
is  poor  practice  to  provide  more  kilns  than  can  be  efficiently 
used,  but  this  is  seldom  done.  Very  often  it  is  the  reverse. 
Kilns  depreciate  heavily  when  not  in  use,  especially  during 
winter  weather. 

CHOICE   OF   EQUIPMENT 

Choosing  the  equipment  for  a  plant  is  a  very  difficult  job 
for  the  inexperienced  and  almost  as  difficult  for  a  clay- 
worker  entering  a  new  line. 

The  clay  machinery  manufacturers  have  greatly  improved 
their  equipment  in  the  past  few  years  and  it  is  not  now 
a  question  of  getting  good  equipment  so  much  as  the  proper 
selection. 

Very  often  the  prospective  purchaser  is  forced  to  deal 
with  men  who  have  no  engineering  knowledge  and  who 
know  as  little  about  his  requirements  as  he  knows  himself, 
sometimes  less.  The  purchase  of  equipment  on  a  purely 
price  basis  has  also  gotten  many  plants  into  difficulties  at 
the  very  beginning. 

When  not  thoroly  familiar  with  the  requirements,  a  clay- 
worker  or  prospective  clayworker  should  consult  either  an 
engineer  or  another  clayworker  who  is  familiar  with  the 
product,  before  reaching  a  decision.  This  is  extremely  im- 
portant as  it  can  safely  be  said  that  the  great  majority  of 
new  plants  have  in  the  past  been  greatly  handicapped  b? 
purchasing  unsuitable  equipment.  It  is  generally  the  one 
great  desire  of  experienced  clayworkers  that  they  have  the 
opportunity  of  rebuilding  their  plants  in  order  that  the  origi- 
nal errors  might  be  eliminated. 

STORAGE   OF   RAW    MATERIAL 

Very  seldom  is  a  plant  originally  equipped  with  proper 
storage  facilities.  If  a  plant  is  to  operate  the  entire  year 
this  is  practically  always  essential.  In  cold  climates  frozen 
clay  or  shale  is  encountered  during  the  winter  and  in  warmer 
climates  the  winter  season  is  generally  wet.  Rainy  days 
will  drive  a  clay  or  shale  pit  crew  from  their  work  and  this 
compels  a  shutdown  with  attendant  losses.  Of  course,  where 
clay  is  mined  underground  a  storage  is  not  so  essential. 

It  is  not  necessary  to  have  an  expensive  storage  shed  or 
building  as  even  an  open  building,  simply  roofed  over,  will 
serve  the  purpose. 


Suggestions  on  Location  and  Design  185 

As  a  rule,  with  good  management,  a  clay  or  shale  pit 
can  be  operated  a  great  deal  during  the  winter  months  and 
if  only  a  storage  building  for  minimum  requirements  can  be 
afforded  it  is  necessary  only  to  figure  on  capacity  sufficient 
to  carry  the  plant  over  protracted  cold  or  wet  spells.  As  the 
men  who  usually  handle  the  pit  can  be  used  in  the  shed 
when  it  is  necessary  to  draw  on  the  storage,  equipment  for 
mechanical  handling  is  not  necessary,  altho  when  the  situa- 
tion warrants  it,  it  is  usually  a  good  investment. 

DRYING   EQUIPMENT  AND   BURNING  SYSTEM 

There  are  four  systems  of  drying  available — mechanical, 
waste  heat,  direct  fired  and  waste  steam. 

The  mechanical  dryer  is  an  expensive  installation  and 
should  be  used  in  connection  with  the  manufacture  of  high 
priced  products  such  as  refractories,  in  preference  to  all 
others. 

The  waste  heat  dryer,  using  heat  from  cooling  kilns,  is 
the  most  popular  system  and  where  heat  can  be  drawn  from  a 
sufficient  number  of  kilns,  it  is  economical  and  generally  suc- 
cessful. Where  few  kilns  are  available  and  it  is  necessary 
to  resort  to  an  auxiliary  furnace  for  sufficient  heat,  the  sys- 
tem becomes  uneconomical  and  dirty.  Practically  any  type 
of  product  can  be  dried  by  this  system  when  it  is  intelli- 
gently handled  and  under  proper  control. 

Direct  heat  dryers  or  those  provided  with  a  furnace  un- 
der each  tunnel  are  also  popular  and  very  successful  with 
any  type  of  product.  The  control  of  this  type  is  almost  per- 
fect, but  when  a  quantity  of  waste  heat  is  available  and  is 
not  used  it  is  undoubtedly  the  more  expensive  to  operate. 

Waste  steam  dryers  are  not  now  used  as  much  as  for- 
merly, due  to  the  heavy  upkeep  and  the  fact  that  live  steam 
has  to  be  furnished  during  the  hours  when  the  plant  is  not 
producing  ware,  and  the  engine  running.  This  makes  the 
drying  cost  high. 

The  selection  of  one  of  the  systems  must  be  made  after 
taking  into  consideration  the  raw  material,  the  product,  waste 
heat  available  and  its  source,  and  the  price  of  fuel.  Con- 
sultation on  this  matter  with  those  having  experience  will 
also  pay  in  the  long  run. 

The  selection  of  a  burning  system  is  so  bound  up  with 
the  product,  location  of  plant,  fuel  available  and  size  of  plant 
that  in  this  case  also,  it  is  a  question  that  should  be  very 
thoroly  investigated  before  a  decision  is  reached.  The 


186     Clay  Plant  Construction  and  Operation 

systems  available  are  the  scove  or  open  top,  the  down  draft, 
the  continuous  and  the  railroad  tunnel  kiln. 

It  would  require  a  chapter  to  go  into  the  merits  of  these 
various  types.  It  is  sufficient  to  say,  therefore,  that  the  type 
in  most  successful  and  general  use  in  the  vicinity  of  the 
proposed  plant,  and  in  use  on  the  same  type  of  product, 
will  usually  be  the  safe  type  to  select.  This  again  is  a 
question  that  should  be  referred  to  an  authority  before 
reaching  a  decision  as  each  plant  presents  a  problem  in  it- 
self. 

LAYING  OUT  THE  PLANT 

It  is  almost  impossible  to  use  standard  plans  in  laying 
out  a  plant,  but  the  method  herewith  presented  will  make 
it  fairly  easy  for  a  man  with  very  little  mechanical  ability 
to  handle  the  planning  successfully. 

After  the  equipment,  dryers  and  type  and  number  of  kilns 
has  been  fully  decided  upon  a  small  drawing,  absolutely  to 
scale,  should  be  made  of  the  plan  (floor  area  occupied)  of 
each  machine.  The  dimensions  should  be  taken  from  blue- 
prints furnished  by  the  machinery  companies.  Similar  draw- 
ings, always  to  the  same  scale,  should  be  made  of  the 
motors,  engines  and  boilers,  in  fact  this  must  be  done  for 
each  and  every  piece  of  equipment  that  goes  into  the  fac- 
tory. The  dryers  and  kilns  should  be  handled  in  the  same 
manner,  a  separate  drawing  being  made  for  each  tunnel 
and  kiln. 

When  these  are  completed,  each  drawing  should  be  cut 
out  along  the  exterior  lines.  With  the  aid  of  an  architect's 
scale  they  can  then  be  arranged  on  a  large  sheet  of  paper 
in  any  manner  that  suits  the  fancy  and  when  finally  a  lay- 
out that  appears  to  be  the  most  compact  and  efficient  has 
been  arrived  at,  the  outline  of  the  buildings,  tracks,  switches, 
etc.,  can  be  sketched  in  around  them.  The  beauty  of  this 
arrangement  is  that  any  number  of  different  arrangements 
may  be  tried  by  merely  shuffling  the  small  drawing  around 
and  the  defects  in  each  arrangement  studied.  By  this  method 
also  it  is  very  easy  to  allow  for  the  proper  clearance  around 
each  piece  of  equipment,  the  proper  pulley  centers  and 
to  avoid  crowding,  as  well  as  to  tell  at  a  glance  whether 
or  not  the  material  is  kept  constantly  flowing  in  one  direction 
without  any  "back  tracking." 

By  making  an  extra  set  of  these  small  outline  plans  and 
using  a  surveyed  plan  of  the  property  the  proper  provisions 
for  future  growth  can  be  made. 


Suggestions  on  Location  and  Design  187 

This  method  will  be  found  vastly  superior  to  that  of  lay- 
ing out  a  plant  along  the  lines  of  another  seen  elsewhere  or 
according  to  a  single  preconceived  idea,  as  seldom,  in  such 
cases,  does  it  happen  that  the  mistakes  are  found  until  the 
plant  is  ready  for  operation. 

BUILDINGS    SHOULD    ADMIT    PLENTY    LIGHT 

During  recent  years  the  type  of  building  erected  by  the 
clayworker  has  been  a  vast  improvement  over  those  of  a 
few  years  ago. 

There  is  really  no  reason  why  a  clay  products  plant  should 
not  have  buildings  of  a  modern  factory  type.  As  the  manu- 
facturer of  the  best  of  structural  products,  the  buildings 
should  really  be  an  advertisement.  The  elimination  of  fire 
risk  is  also  an  important  item.  Being  almost  always  of  the 
single  story  type  there  need  be  little  lumber  used  and  that 
only  in  the  roof  trusses. 

Light  buildings  are  almost  essential  if  a  good  product  is  to 
be  made,  and  as  it  is  as  cheap  to  put  in  sash  and  glass  as  to 
fill  the  same  space  with  brick,  plenty  of  light  and  air  should 
be  provided. 

POWER   CONSIDERATIONS 

A  few  words  on  the  subject  of  power  may  be  of  value. 
The  time  has  arrived  or  is  rapidly  approaching  when  power 
can  be  purchased  in  almost  any  part  of  the  country  cheaper 
than  it  can  be  produced  in  a  small  factory  steam  plant. 

In  deciding  the  question  as  to  the  power  that  will  be  used 
a  balance  must  be  made  between  the  individual  plant  and 
purchased  power.  On  the  individual  plant  the  installation  of 
boilers,  engine,  shafting,  pulleys  and  feed  water  pumps  are 
part  of  the  original  investment,  with  fixed  charges  for  the 
services  of  engineers,  fuel,  fuel  handling  and  boiler  com- 
pounds additional.  Against  this  there  is  the  cost  of  pur- 
chased power  and  the  motors.  Installation  expense  and 
repairs  are  not  taken  into  consideration,  but  they  will  be  in 
favor  of  purchased  power. 

Aside  from  the  above  a  great  deal  of  consideration  must 
be  given  to  the  flexibility  of  motor  drives.  A  far  more  flex- 
ible and  compact  plant  can  be  built  and  generally  with  a 
saving  on  building  cost.  In  addition  troublesome  belts  can 
be  replaced  by  chain  drives  and  line  and  counter  shafting, 
which  is  always  a  nuisance,  can  be  done  away  with.  Before 
a  decision  is  reached  all  these  items  should  be  carefully  con- 
sidered. 


188     Clay  Plant  Construction  and  Operation 

CONSTRUCTION    OF    PLANT 

One  of  the  peculiarities  of  the  clay  industry  is  that  it  is 
probably  the  only  large  industry  known  in  which  the  plant 
operators  attempt  to  do  their  own  construction.  This  is 
stranger,  too,  when  it  is  considered  that  so  many  clay  plant 
managers  and  superintendents  know  absolutely  nothing  about 
building  construction.  Plenty  of  proof  of  this  is  seen  in 
the  many  clumsy,  dark,  unhandy  plants  that  are  seen  on 
every  side. 

Building  construction  is  a  business  in  itself,  and  in  most 
cases  should  be  left  to  those  who  know  it.  Why  the  clay- 
worker  is  unwilling  to  turn  the  construction  of  his  plant 
over  to  a  reliable  contractor  is  hard  to  determine.  The  con- 
tractor will  certainly  make  a  profit  on  the  job,  but  even 
allowing  for  this,  it  is  safe  to  say  that  the  job  will  cost  less 
and  be  done  better  than  if  he  attempts  it  himself.  The  larger 
and  better  managed  companies  are  putting  their  construction 
work  in  the  hands  of  reliable  firms,  but  the  smaller  companies 
still  seem  to  hesitate  about  doing  so. 

There  can  be  no  question  about  the  advisability  of  letting 
plant  construction  out  on  contract,  especially  as  the  con- 
tracting business  has  reached  a  high  plane.  Very  often  the 
contractor,  thru  his  experience,  can  point  out  various  im- 
provements that  can  be  made  in  the  plans,  and  if  the  contract 
is  on  a  time  and  material  basis  plus  a  percentage,  he  can 
very  often  secure  the  materials  cheaper  than  can  an  outsider. 

While  it  is  advisable  to  contract  the  construction  of  the 
buildings  proper,  it  is  always  advisable  for  the  clayworker 
to  take  charge  of  the  setting  of  his  equipment  (providing  he 
is  capable  of  doing  so),  and  the  construction  of  the  kilns. 
Kilns  built  on  contract  are  usually  unsatisfactory,  and  as  they 
represent  a  large  part  of  the  investment  and  much  depends 
on  them,  great  care  should  always  be  exercised  in  their 
erection. 


CHAPTER  XVII 


Caring  for  Equipment 


/CAPACITY  IS  THE  TURNING  POINT  on  which  the 
^*  success  or  failure  of  a  clayworking  plant  depends.  In 
this  article  "capacity"  must  not  be  confused  with  "output," 
but  is  to  be  defined  as  the  maximum  amount  of  material  it 
is  possible  to  put  thru  the  weakest  unit  of  a  plant  per  day 
or  per  year.  Very  generally  the  weak  units  of  a  plant  (or 
the  units  which  have  the  smallest  capacity)  are  either  the 
dryers  or  the  kilns,  and  in  such  cases  these  units  regulate 
the  capacity. 

Most  clayworkers  realize  that  in  order  to  be  successful, 
or  in  other  words,  to  pay  dividends,  it  is  absolutely  neces- 
sary that  the  plant  be  continuously  run  to  "capacity."  However, 
from  the  annual  record  of  failures  in  the  clayworking  in- 
dustry it  is  quite  plain  that  whether  the  importance  of  this 
fact  is  realized  fully  or  not,  the  plant  owners  who  are  able 
to  continuously  get  "capacity"  are  in  the  minority. 

The  writer  could  readily  name  a  dozen  men  who  stand 
head  and  shoulders  above  their  fellows  in  the  industry,  and 
whose  very  names  spell  success ;  it  takes  but  a  moment  to 
analyze  the  reason.  In  few  words — it  is  because  they  can 
get  "capacity" — every  ounce  of  capacity  out  of  their  plants, 
day  after  day,  month  after  month  and  year  after  year. 

It  goes  almost  without  saying  that  men  who  can  accom- 
plish this  result  have  very  little  trouble  as  regards  quality, 
and  very  little  trouble  in  the  disposal  of  their  products,  the 
same  rule  being  reversed  and  working  the  other  way  equally 
as  well ;  men  who  handle  a  plant  in  such  a  way  that  break- 
downs and  shut-downs  are  the  regular  thing,  cannot  keep  up 
the  quality  and  cannot  dispose  of  their  products  with  the  same 
tase  as  the  men  whose  plants  are  run  to  "capacity"  from  one 
year's  end  to  another. 

In  no  other  industry  are  excuses  for  failure  so  readily 
189 


190     Clay  Plant  Construction  and  Operation 

accepted;  yet  who  can  point  to  a.  leader  in  the  field  of  clay- 
working  who  has  not,  at  some  time  or  other,  taken  hold  of 
a  plant  which  has  been  a  financial  failure  in  other  hands 
and,  by  waving  the  magic  wand  of  his  efficiency,  has  brought 
it  back  to  prosperity.  Often  this  is  done  without  the  change 
or  addition  of  a  single  piece  of  equipment.  When  investi- 
gation sought  the  reason  for  the  financial  reform,  it  found — 
it  always  finds — capacity. 

What  are  the  reasons  for  some  plants  running  with  a 
steady  output,  while  others,  equally  well  situated,  are  unable 
to  do  so?  In  the  first  place  it  is  absolutely  necessary  that 
the  machinery  equipment  be  of  the  highest  grade  and  suited 
to  the  materials  and  process ;  that  the  various  units  which 
make  up  the  plant — mining,  manufacturing,  drying  and  burn- 
ing— be  well  balanced ;  that  there  be  harmony  among  the 
employes  and  that  the  man  in  charge  be  thoroly  capable  of 
keeping  his  equipment  in  first-class  condition.* 

WELL    BUILT    MACHINERY    A    PRIME    NECESSITY 

The  quality  and  type  of  the  machinery  is  of  prime  import- 
ance. With  weak,  poorly  designed  and  poorly  built  machin- 
ery, or  machinery  that  is  unsuitable  for  the  work  required, 
nothing  but  trouble  can  be  expected.  A  plant  is  often  doomed 
by  the  machinery  salesman  before  it  is  built ;  and  here  our 
industry  in  unique,  for  in  no  other  can  equipment  be  found 
that  is  so  totally  unfit  for  the  service  required  of  it.  It  is 
useless  to  blame  the  machinery  manufacturer  altogether,  for 
he  is  merely  supplying  the  market  with  what  it  demands  and 
at  the  price  it  is  willing  to  pay. 

Where  it  is  practically  impossible  to  get  efficiency  out  of  a 
plant  because  its  equipment  is  not  equal  to  the  work  required 
of  it,  there  can  be  but  one  wise  thing  to  do,  and  that  is  to 
eliminate  the  weak  parts  and  replace  them  with  units  of  suffi- 
cient strength.  It  is  often  a  single  machine  that  causes  the 
trouble,  a  dry-pan,  elevator,  pug-mill,  brick-machine  or  cut- 
ter, involving  the  expenditure  of  a  thousand-  dollars  or  less, 
an  amount  easily  lost  every  month  or  two  in  a  plant  constant- 
ly bothered  with  break-downs.  As  an  illustration  of  this — 
the  writer  recently  had  occasion  to  go  thru  a  very  successful 
Ohio  plant  with  a  party  of  business  men ;  pushed  into  an 
out-of-the-way  corner  was  a  complete  and  very  fair  looking 
hollow-ware  machine.  The  president  of  the  company  was 
asked  why  the  machine  had  been  thrown  out.  His  laconic 
reply  was  that  "It  was  not  a  dividend  producer"  It  appeared 
that  a  smaller,  but  better  designed  machine  which  had  taken 


Caring  for  Equipment  191 

its  place,  was  producing  fifty  per  cent  more  tonnage — not  be- 
cause the  ware  was  pushed  out  faster  but  because  the  ma- 
chine ran  without  constantly  recurring  mechanical  troubles. 
A  plant  to  run  efficiently  should  be  well  balanced.  It  is 
far  easier  to  keep  up  a  steady  flow  of  ware  if  the  dryer 
easily  takes  care  of  the  machine,  and  the  kilns  easily  take 
care  of  the  driers.  Moreover,  a  halting,  unsteady  flow  of 
ware  will  demoralize  the  best  gang  of  men  that  ever  worked 
in  a  brick  plant. 

HARMONY   AMONG    EMPLOYES   AN    ESSENTIAL    FEATURE 

Harmony  among  the  employes  is  a  very  important  factor. 
This  is  especially  true  with  regard  to  the  foremen  and  me- 
chanics. Foremen  who  work  together  and  who  constantly 
assist  one  another  can  do  wonders  toward  getting  capacity. 
One  foreman  or  (to  a  lesser  extent)  one  laborer  who,  either 
thru  inefficiency  or  pure  cussedness,  is  out  of  step  with  the 
organization,  can  do  quite  as  much  harm  as  a  weak  machine 
— probably  more. 

Granting  that  a  plant  is  equipped  with  good  machinery,  is 
well  balanced  and  has  an  efficient  organization,  what  more  is 
necessary  to  keep  it  running  to  capacity?  The  answer  is — 
the  prevention  of  break-downs  and  the  ability  to  make  quick 
repairs.  Therein  lies  the  secret  of  success.  No  machine  is 
so  strongly  built  that  it  will  not  wear  out  and  break  down 
— if  allowed  to  do  so. 

The  break-downs  that  are  due  to  unpreventable  accidents, 
can  and  should  be  reduced  to  a  minimum.  Preparedness  will 
reduce  the  loss  due  to  such  accidents  to  a  point  where  they 
are  unimportant.  It  is  with  preparedness  then  that  this 
article  will  principally  deal,  altho  the  prevention  of  break- 
downs and  shut-downs  will  receive  considerable  attention. 

FINDING    THE    WEAK    POINTS 

The  first  six  months  after  a  new  plant  has  commenced 
operations  will  develop  practically  all  of  the  weak  points. 
One  of  the  invariable  rules  a  manager  or  superintendent 
should  make  on  a  new  plant,  or  a  new  manager  or  super- 
intendent on  an  old  plant,  is  to  never  allow  any  sinnlc 
part  to  break  or  cause  trouble  twice  in  the  same  place,  with- 
out making  an  effort  to  strengthen  the  part.  A  part  may 
break  once,  and  the  break  be  due  to  flaws,  carelessness,  or 
other  reasons  over  which  there  is  little  control  and  it  may 
not  be  necessary  to  strengthen  it — but  if  the  same  thing  hap- 


192     Clay  Plant  Construction  and  Operation 

pens  twice,  there  is  seldom  any  other  reason  than  inability 
to  stand  up  to  the  work  required.  In  the  vast  majority  of 
cases,  strengthening  a  part  can  be  done  without  very  much 
extra  expense,  and  in  any  case  with  less  expense  than  the 
loss  incurred  by  constant  shut-downs  and  consequent  de- 
creased output. 

As  an  example  of  strengthening  a  piece  of  equipment,  the 
following  is  cited.  The  pugging  shaft  on  a  long  pug-mill  broke 
where  the  hex  portion  was  turned  down  to  pass  thru  the 
marine  thrust.  A  new  shaft  was  ordered  by  express.  Dur- 
ing the  interval  of  several  days  between  the  time  of  the 
break  and  the  arrival  of  the  new  shaft,  half  of  the  plant 
was  shut  down.  Within  a  week  after  Jhe  new  shaft  was  put 
in,  it  broke  in  exactly  the  same  place  as  the  first.  Such 
breakages  might  have  kept  up  indefinitely,  but  when  the 
second  shaft  broke,  the  hex  portion  of  it  was  taken  to  a 
forge  shop  and  a  piece  of  ordinary  cold  rolled  shafting,  one- 
half  of  an  inch  larger  in  diameter  than  the  original,  was 
welded  to  it.  The  thrust  rings  were  bored  out  to  fit  the  new 
shaft  and  the  bearings  rebabbitted  to  take  the  larger  diameter. 
There  has  not  been  a  particle  of  trouble  with  that  machine 
since. 

In  another  instance  the  knife  holders  on  a  pug-mill  shaft 
would  break  off  near  the  hub,  allowing  a  knife  to  drop  to  the 
bottom  of  the  mill.  This  generally  resulted  in  the  breaking 
of  several  more,  due  to  contact  with  the  broken  piece.  A 
pattern  was  made,  providing  l/4  in.  more  metal  all  over,  with  a 
heavy  fillet  at  the  weak  point.  The  trouble  ceased  at  once. 

In  still  another  instance  the  cast-iron  ring  or  front  piece, 
to  which  the  dies  are  fastened  on  a  hollow-ware  machine, 
broke.  Another  was  procured  and  the  same  results  followed, 
due  to  accidental  stiffening  of  the  clay.  Instead  of  duplicat- 
ing this  front  a  third  time,  a  steel  one  was  made.  The 
trouble  never  occurred  again. 

SOME    PLANTS    SEEM    TO    "GET    TIRED" 

These  instances  are  cited  merely  to  illustrate  the  point  that 
if  a  weak  point  in  the  equipment  is  found,  it  is,  as  a  gen- 
eral rule,  a  very  easy  and  inexpensive  matter  to  strengthen 
it.  Time  and  again  the  author  has  come  in  contact  with 
plants  where  no  effort  is  made  to  overcome  a  weakness  of 
this  kind.  Possibly  a  duplicate  part  is  kept  in  stock  and  put 
in  when  necessary,  or  else  the  express  company  is  called 
upon,  while  the  plant  shuts  down. 


Caring  for  Equipment  193 

The  author  has  in  mind  a  plant  which  is  operating  a  very 
troublesome  machine.  All  of  the  trouble  is  caused  by  the 
constant  breaking  of  a  very  light  shaft.  This  shaft  has 
broken  twice  in  a  single  day  and  seldom  lasts  more  than  a 
few  weeks.  Yet  no  effort  has  ever  been  made  to  eliminate 
the  cause  of  the  trouble,  altho  an  extra  shaft  always 
lies  beside  the  machine  ready  for  instant  use.  In  this  day 
of  special  steels  it  would  not  even  be  necessary  to  increase 
the  diameter  of  that  particular  shaft,  altho  it  might  be 
necessary  to  have  one  rolled  to  order.  But  special  steel 
would  eliminate  the  trouble. 

Some  clayworkers  would  do  well  to  examine  the  gears  and 
shafting  of  a  fifty  or  sixty  h.  p.  motor-truck,  and  then  con- 
sider that  small  as  they  are,  they  are  called  upon  to  convey 
as  much  power  as  the  gears  and  shafts  on  some  claywork- 
ing  machines,  altho  they  are  only  from  one-tenth  to  one- 
third  the  size.  It  is  largely  a  question  of  special  steel. 

Lack  of  initiative  on  the  part  of  the  clayworker  lies,  at 
the  bottom  of  a  great  deal  of  the  trouble.  If  he  cannot 
secure  a  stronger  part  from  the  maker  of  the  machine,  he 
simply  "kicks"  and — keeps  on  buying.  The  proper  method, 
under  the  circumstances,  would  be  to  abandon  the  maker 
whose  machine  parts  show  such  weakness  and  try  elsewhere 
to  have  parts  made  that  will  give  proper  service. 

A  PROPER  SUPPLY  OF  REPAIR  PARTS 

Next  in  importance  to  preventing  the  recurrence  of  an 
accident  by  increasing  the  strength  or  improving  the  design 
of  the  troublesome  part,  is  the  keeping  of  a  supply  of  re- 
pair parts  on  hand.  It  is  much  easier  and  cheaper  to  do 
this,  of  course,  when  the  plant  has  its  own  machine  shop, 
but  it  is  far  more  important  on  the  plant  which  has  none, 
especially  if  a  custom  repair  shop  is  not  easily  accessible. 

If  a  clayworker  does  not  know  what  repair  parts  he  should 
keep  on  hand,  he  soon  learns  thru  "hard  knocks."  When 
once  a  part  gives  trouble,  either  thru  breakage  or  wear, 
he  should  make  it  a  rule  to  always  have  a  duplicate  within 
reach.  This,  of  course,  means  an  investment — probably  a 
large  one — but  it  is  the  best  investment  a  clayworking  plant 
can  make.  A  few  days  shut  down,  with  the  attendant  loss, 
more  than  offsets  the  "economy"  that  prevented  a  stocking  up. 
Some  plants  follow  this  rule,  and  they  generally  arouse  the 
envy  of  their  competitors,  who  constantly  wonder  how  those 
plants  run  with  so  little  apparent  trouble. 


194     Clay  Plant  Construction  and  Operation 

In  the  following,  the  author  will  attempt  to  itemize  the 
troubles  most  generally  encountered  on  any  sort  of  a  clay- 
working  plant,  and  the  remedies  suggested. 

SHALE   OR    CLAY    PIT 

In  the  average  pit  there  is  probably  nothing  that  inter- 
feres with  capacity  so  much  as  tracks.  In  the  nature  of 
things  it  is  hard  to  keep  tracks  in  good  shape,  as  they  are 
often  damaged  by  shots.  Dirt  accumulates  upon  them  and 
in  the  switches  and  frogs.  Thru  this,  empty  and  loaded  cars 
jump  the  tracks  and,  oftentimes,  a  machine  is  kept  waiting 
or  run  under  its  capacity  because  of  the  derailed  car  or  cars. 
In  the  author's  opinion,  more  pit  foremen  have  "fallen  down" 
on  their  jobs  thru  neglecting  their  tracks  than  thru  all  other 
reasons  combined. 

The  tracks  should  be  kept  clean  enough  to  allow  the  flanges 
of  the  wheels  to  clear  at  all  times.  They  should  constantly 
be  kept  to  gauge.  Sharp  curves  should  be  avoided,  for  it  is 
generally  better  to  be  without  them  than  to  put  up  with  the 
trouble  they  give.  The  use  of  twelve  and  sixteen  pound 
rails  causes  much  trouble.  Rails  under  twenty-five  pounds 
should  never  be  used,  except  for  the  temporary  jumpers,  and 
even  there  heavier  rails  save  trouble  in  the  end.  Main  lines, 
which  need  not  be  disturbed,  should  be  laid  with  heavy  rails 
and  heavy  ties.  Even  light  standard  rails  and  standard  ties 
soon  pay  for  themselves  in  such  places. 

The  cars  too,  often  give  trouble  thru  wear,  allowing  the 
wheels  to  either  jump  or  "drop  in."  This  should  be  espe- 
cially watched  and  the  wheels  bushed  or  washered  so  as  to 
keep  them  to  gauge. 

When  shovels  are  used,  either  steam  or  electric,  a  very 
complete  set  of  repair  parts  should  be  kept  on  hand.  The 
nature  of  shovel  work  causes  constant  repairs  and  attention, 
and  unfortunately  the  men  who  handle  them  are  too  often 
of  a  careless  sort.  Wearing  parts  should  be  examined  daily, 
either  by  the  superintendent,  pit  foreman  or  mechanic,  unless 
a  very  reliable  shovel  man  is  in  charge.  Chains,  cables,  bear- 
ings and  teeth  require  particular  attention.  The  pit  foreman 
should  watch  the  face  in  front'  of  the  shovel  at  all  times  to 
prevent  "caves"  that  may  bury  or  injure  the  shovel. 

INCLINE 

If  an  incline  is  used  there  are  several  things  in  connection 
with  its  maintenance  and  operation  that  require  careful  atten- 


Caring  for  Equipment 


195 


tion.  In  the  first  place  the  use  of  a  standard  sixty  pound  rail 
will  do  much  to  prevent  trouble.  Many  plants  operate  a  sys- 
tem in  which  the  empties  are  drawn  up  by  the  descending 
loads.  In  most  cases  of  this  kind  a  hook  on  the  ends  of  the 
cable  is  fastened  to  the  couplings  on  the  cars.  The  chief 
difficulty  encountered  in  this  system  is  that  frequently  the 
hooks  or  couplings  break  while  they  are  on  the  incline,  and 
the  result  is  a  "smash  up"  at  the  bottom.  These  breaks  are 


PIT 


1=^ 

Fig.  77.     Illustrating   the   Use  of  a   "Cage"   in   the    Haulage   System. 

caused  by  the  crystallization  of  the  iron  hock  or  coupling. 
//  the  hooks  and  couplings  are  taken  from  the  rope  and 
cars  once  a  month,  and  put  into  a  large  wood  bonfire  which 
will  heat  them  to  a  dull  red,  and  are  then  allowed  to  remain 
in  the  ashes  until  cool,  this  trouble  will  be  entirely  eliminated. 
It  is  preferable  to  put  them  in  the  fire  on  Saturday  night 
and  allow  them  to  remain  in  the  ashes  until  Monday  morn- 
ing. 

Even  at  best,  any  haulage  system  where  the  cars  run  up 
and  down  an  incline,  is  likely  to  be  troublesome  and  cause 
delays.  A  great  improvement  is  made  by  the  use  of  a  "cage" 
as  shown  in  Figue  77.  This  may  consist  of  a  platform  on 
wheels,  to  which  the  cable  is  permanently  attached.  The 
cars  are  run  onto  this  platform  at  the  top  and  off  at  the 
bottom,  and  vice  versa. 

The  distinct  advantage  of  this  system  over  running  the 
cars  down  the  incline  on  their  own  wheels,  is  that  the  cable 
can  be  securely  and  permanently  attached  to  the  cage.  An 
accident  on  this  sort  of  an  arrangement  is  practically  un- 
heard of,  unless  it  be  thru  the  breaking  of  a  wornout  cable. 


196     Clay  Plant  Construction  and  Operation 

The  cable  and  drum  should  be  thoroly  examined  by  the  fore- 
man each  morning.  Too  much  care  cannot  be  taken  in  this 
department,  as  accidents  are  generally  serious  enough  to  cause 
considerable  damage  or  delay.  A  cable  should  never  be 
allowed  to  "wear  out."  As  soon  as  strands  begin  to  break, 
it  should  be  replaced,  or  cut  and  spliced. 

STORAGE    SHED 

The  storage  shed  should  be  kept  full  of  clay.  If  this  rule 
is  adhered  to,  the  source  of  supply  can  be  cut  off  for  several 
days  or  even  weeks,  thru  accident  or  bad  weather,  and  the 
plant  can  still  run  to  capacity.  Such  things  as  the  burying 
of  steam  shovels,  the  collapse  of  inclines  or  trestles,  the 
burning  out  of  dynamos  and  motors  will  happen,  and  in  such 
cases  the  storage  shed  may  be  a  "life  saver." 

When  conveyors  are  used  in  the  shed,  they  should  be  fre- 
quently examined — especially  the  bearings  on  the  idlers  and 
pulleys.  The  trough  should  be  often  cleaned,  as  the  friction 
frequently  causes  the  belts  to  tear  if  dirt  is  allowed  to  pile 
up  under  them.  All  conveyor  belt  joints  should  be  submitted 
to  daily  examination.  Conveyor  belts  have  a  way  of  tear- 
ing out  at  the  fasteners  without  warning,  and  in  some  plants 
a  break-down  means  a  shut-down  in  the  plant. 

POWER  PLANT 

The  power  plant  very  seldom  causes  a  shut-down,  but  that 
is  no  reason  for  its  being  neglected.  Steam  engines  are  easy 
to  keep  in  first-class  running  order,  principally  because  the 
parts  are  easy  to  see  and  easy  to  get  at.  It  is  an  excellent 
rule  to  have  the  cylinder  head  occasionally  taken  off,  in  or- 
der to  see  that  the  large  nut  which  holds  the  piston  on  is 
tight,  and  that  the  piston  rings  are  intact.  When  an  accident 
does  happen  to  the  engine  it  is  serious,  and  attention  given 
to  prevention  is  well  worth  while. 

Boilers  are  little  likely  to  prove  troublesome  if  intelligently 
handled.  The  accidents  that  generally  happen  to  them  are 
cracks  in  the  sheets,  blisters,  open  seams  and  leaky  rivet 
holes.  All  of  these  things  are  due  to  carelessness.  Plant 
operators  are  too  much  inclined  to  leave  this  department  to 
take  care  of  itself.  A  glance  thru  the  boilers  at  the  time  of 
washing  out  takes  but  a  moment  and  should  always  be  done 
by  the  superintendent.  Intelligent  firing  avoids  the  other 
difficulties. 

THE    CARE    OF    MOTORS 

When  electric  current  is  used,  the  motors  require  careful 


Caring  for  Equipment  197 

attention.  The  motor  is  rather  a  new  tool  in  the  hands  of 
the  clayworker — something  out  of  his  line.  He  is  inclined 
to  look  upon  it  as  something  with  which  he  is  anything  but 
familiar — and  therefore  to  be  left  strictly  alone — or  a  con- 
trivance so  wonderfully  self-contained  that  no  particular 
attention  need  be  given  it.  Seldom  are  experienced  elec- 
tricians emjloyed  on  a  clay  working  plant,  but  it  will  pay 
to  encourage  someone  to  make  a  study  of  motors  and  then 
give  him  charge  of  that  part  of  your  equipment.  The  fact  is, 
a  motor  does  need  intelligent  care  if  it  is  not  going  to  prove 
a  big  expense. 

The  bearings  are  the  principal  source  of  trouble.  Bearing 
trouble  leads  to  all  of  the  other  troubles,  causing  grounding 
of  the  field  coils,  charring  of  the  insulation,  etc. 

The  bearings  should  be  emptied  of  oil  at  least  once  each 
month  and  then  thoroly  washed  out  with  kerosene.  The  old 
oil  should  not  be  put  back  (unless  it  is  filtered),  but  new 
oil  used  each  time.  The  air  gap  between  armature  and  field 
should  be  constantly  examined,  and  as  soon  as  it  is  seen  to 
be  closing  on  the  bottom,  the  bearings  should  be  adjusted  or 
new  ones  put  in. 

It  is  the  neglect  of  this  air  gap  that  causes  nearly  all  "burn 
outs."  As  soon  as  the  armature  comes  in  contact  with  the 
field,  the  friction  causes  heat,  which  in  turn  burns  the  insula- 
tion and  causes  the  machine  to  "ground." 

On  most  motors,  especially  large  ones,  there  are  adjusting 
nuts  on  the  under  side  of  the  frame.  As  the  bearings  wear 
and  the  armature  drops,  these  nuts  should  be  taken  up.  This 
increases  the  air  gap  at  the  bottom. 

When  all  the  adjustment  is  taken  up  (and  it  only  amounts 
to  about  one-eighth  of  an  inch)  new  bearings  should  be  put 
in  at  once. 

As  clay-plant  motors  are  generally  in  dusty  places,  they 
should  be  regularly  blown  out  with  a  hand  bellows.  Dust 
accumulating  in  the  coils  and  between  the  armature  bars, 
especially  if  it  gets  damp  after  standing,  will  sometimes  cause 
serious  trouble.  Motors  when  receiving  regular  attention 
never  give  trouble.  It  pays  to  look  after  them,  for  the  burn- 
ing out  of  a  single  motor  often  ties  up  a  plant. 


CHAPTER  XVIII 


Running  a  Plant  to  Capacity 


npHE  TROUBLESOME  POINTS  about  a  pan  are  the 
•*•  scrapers,  screen-plates,  step  and  clutch.  The  scrapers 
are  subjected  to  especially  hard  service,  where  hard,  lumpy 
shales  or  damp  sticky  clay  are  used.  Often  in  such  cases, 
those  which  originally  come  with  the  pan  are  not  strong 
enough,  or  are  not  set  at  the  proper  angle  for  the  particular 
material.  When  necessary  heavier  ones  should  be  put  in.  The 
"shoes"  or  replaceable,  adjustable  plates  on  the  front  of  the 
scrapers  should  always  be  kept  at  a  point  where  they  just  clear 
the  screen  plates  (about  one-quarter  of  an  inch).  More  screen 
plates  are  broken  and  scrapers  torn  off  by  their  being  kept  up 
too  high  than  thru  any  other  cause.  Wedge  shaped  pieces  of 
shale  get  between  the  plates  and  scrapers  and  something  must 
give  away  as  the  revolution  of  the  pan  drives  the  wedge  fur- 
ther in.  It  is  generally  the  screen  plates  that  are  broken, 
altho  sometimes  the  scraper  is  torn  off.  In  one  instance  a 
large  plant  was  known  to  have  broken  from  three  to  ten 
screen  plates  per  day  for  a  considerable  period  before  it 
was  discovered  that  the  scrapers  were  being  carried  too  high. 
Aside  from  this,  a  "close"  scraper  keeps  the  pan  bottom  clean 
and  gives  maximum  grinding  capacity. 

It  is  important  that  the  scrapers  have  a  long  sweep  from 
the  muller  to  the  rim.  Short  scrapers  are  subjected  to  a  far 
greater  strain,  both  from  the  friction  of  the  bottom  and  the 
blows  from  lumps,  than  a  long  sweeping  scraper,  and  the 
former  give  far  greater  trouble. 

The  underscrapers,  or  scrapers  under  the  pan,  should  re- 
ceive most  careful  attention.  These  are  so  situated  that  it 
is  extremely  hard  to  examine  them  without  considerable 
trouble,  and  consequently  they  are  neglected.  When  one  of 
these  is  loosened  up,  thru  nuts  dropping  off  or  bolts  break- 
ing, it  generally  means  broken  pan  arms  and  screen  plates, 
or  torn  up  bottoms  and  chutes.  The  use  of  spring  washers 

198 


Running  a  Plant  to  Capacity         199 

under  every  nut,  and  regular  inspection  will  practically  elim- 
inate trouble  from  this  source. 

Screen  plates  are  often  a  source  of  trouble  and  expense  to 
a  plant.  Besides  being  careful  to  keep  the  scrapers  down, 
great  care  should  be  taken  to  keep  the  mullers  from  running 
even  a  fraction  of  an  inch  over  on  the  screen  plates.  If  they 
are  allowed  to  do  so,  and  a  piece  of  shale  or  other  hard 
material  happens  to  be  even  partly  resting  on  a  screen  plate, 
the  direct  pressure  transmitted  to  the  screen  plate  will  likely 
crack  or  break  it. 

In  some  cases,  even  the  utmost  care  will  not  allow  the  use 
of  cast-iron  screens,  on  account  of  the  excessive  breakage. 
It  is  then  wise  to  resort  to  malleable  iron.  These  are  ex- 
pensive but  they  are  practically  unbreakable  and  give  far  bet- 
ter service  than  the  alloy  plates  which  cost  about  the  same. 

HOW    TO   CARE    FOR    PAN    STEP 

Some  plants  are  greatly  troubled  with  pan  steps.  Lack  of 
proper  attention  has  more  to  do  with  this,  than  has  the  type 
of  the  step.  Besides  being  subjected  to  an  excessively  hard 
service,  the  step  is  located  in  a  dusty  place,  and  it  is  gen- 
erally the  dust  and  lack  of  proper  lubrication  that  causes 
difficulties.  Most  steps  are  not  properly  protected  from  dust 
i.  e.,  are  not  tightly  enclosed.  At  small  expense  the  dust-cap 
can  generally  be  fitted  so  that  packing  can  be  inserted  around 
the  shaft  in  the  same  manner  as  in  the  stuffing  box  of  a  pump 
or  engine  cylinder. 

Another  method  is  to  fasten  a  flat  or  umbrella  shaped  cir- 
cular plate  tightly  around  the  shaft,  just  above  the  dust-cap, 
as  shown  in  Fig.  78. 

Dust  falling  on  this  plate  will  be  thrown  clear  by  centrif- 
ugal force.  It  often  happens  that,  when  steps  are  sent  out 
of  the  factory,  they  are  not  provided  with  proper  lubricat- 
ing facilities.  Small  pipes  or  grease  cups  are  generally  pro- 
vided, but  they  soon  become  clogged  at  the  inside  end  with 
dust,  heavy  oil  or  metal  particles.  In  such  cases,  the  man 
who  oils  may  think  he  is  feeding  plenty  of  lubricant,  or  that 
the  step  is  not  using  it  very  fast,  whereas  it  is  getting  little 
or  nothing.  An  inch-and-a-quarter  or  an  inch-and-a  half 
feed  pipe,  provided  with  a  cap,  will  overcome  this  diffi- 
culty. If  this  pipe  is  brought  up  to  the  floor  level  of  the 
factory  or  high  enough  to  give  it  a  "head,"  and  the  step 
housing  made  oil  tight,  the  step  can  run  on  oil  under  a 
slight  pressure. 


200     Clay  Plant  Construction  and  Operation 

An  extra  step  should  always  be  kept  on  hand,  and  the  steps 
in  use  should  be  regularly  examined — at  least  once  each 
month. 


Fig.  78.     Step  Protector. 

The   clutch,   always   important   on   any   machine   should  be 
particularly  well  looked  after  on  the  pans.  Unless  a  pan  can 


Running  a  Plant  to  Capacity         201 

be  stopped  quickly,  great  damage  may  result  from  what  other- 
wise would  be  a  trifling  accident.  On  many  plants,  any  one 
who  sees  fit  to  do  so  can  "monkey"  with  the  clutches  in  an 
effort  to  "adjust"  them.  As  a  consequence  they  are  constantly 
giving  trouble,  and  continually  being  "cussed."  The  author  has 
known  a  plant  to  be  shut  down  for  a  week  simply  because  a 
clutch  would  not  f(throw  out."  Clutches  are  generally  simple 
affairs  and  most  of  them  will  give  efficient  service  if  properly 
handled. 

The  superintendent  should  himself  adjust  the  pan  clutches 
and  all  other  clutches  about  the  plant,  or  should  delegate  his 
mechanic,  a  foreman  or  some  other  thoroly  capable  man  to 
do.  so,  and  should  forbid  others  to  touch  them.  Such  a  rule 
may  cause  a  few  minutes  delay  at  times,  but  will  pay  in  the 
long  run,  and  on  any  plant. 

Bushings  in  the  loose  pulleys  are  likely  to  give  trouble  when 
not  given  sufficient  lubrication.  Careful  attention  should  be 
given  them  and  a  duplicate  for  each  pulley  should  be  kept 
constantly  ready  for  use. 

Crown  wheels  and  pinions  seldom  give  trouble,  but  occa- 
sionally one  will  be  broken  by  a  sudden  jar  from  a  hard  lump 
in  the  pan.  It  is  a  very  good  policy  to  have  extras  on  hand. 

ELEVATORS 

When  an  elevator  causes  constant  shut-downs — and  there 
are  many  such — the  trouble  may  be  due  to  a  number  of 
causes,  all  of  which  can  be  remedied.  In  the  first  place,  most 
clay  plant  elevators  are  not  designed  correctly,  consequently 
trouble  is  to  be  expected,  and  undoubtedly  will  continue  until 
the  proper  remedy  is  applied,  which  is  rebuilding.  Some 
of  the  things  that  cause  elevator  trouble  are :  improper  spac- 
ing of  the  buckets;  undersized  head  pulley;  too  slow  or  too 
great  speed;  incorrectly  designed  discharge  chute;  incor- 
rectly designed  feeding  chute ;  loose  belts  and  failure  to 
clean  out  the  boots. 

Buckets  should  be  spaced  on  eighteen  inch  centers,  and  for 
a  nine  foot  pan,  should  not  be  less  than  six  inches  by  twelve 
inches  in  size. 

Small  head  pulleys  are  often  a  most  serious  source  of 
trouble.  When  the  head  pulley  is  too  small,  the  ascending 
buckets  will  invariably  throw  part  of  their  load  into  the  air 
when  they  strike  the  pulley  and  start  over.  This  is  due  to 
the  abrupt  change  of  direction,  the  dust  being  thrown  up- 
wards by  centrifugal  force.  A  large  percentage  of  the  ma- 


202     Clay  Plant  Construction  and  Operation 

terial  thus  thrown  out  falls  to  the  boot  and  requires  re- 
hoisting,  thereby  at  times  overloading  the  elevator  and  chok- 
ing it.  Standard  construction  requires  that  the  head  pulley 
be  thirty-six  inches  in  diameter.  Large  pulleys,  and  belts 
traveling  at  the  proper  speed,  absolutely  insure  the  material 
remaining  in  the  buckets  until  the  proper  point  of  discharge 
is  reached. 

The  proper  belt  speed  for  an  elevator  of  standard  design 
is  325  feet  per  minute.  This  speed  is  taken  from  the  average 
dry  shale.  It  may  vary  as  much  as  thirty  feet  either  way 


T 


on  some  materials,  but  with  this  speed  as  a  starting  point, 
experiment  will  determine  the  proper  speed  for  any  particular 
material. 

The  discharge  chute  may  be  too  high  or  too  far  away  from 
the  buckets.  These  defects  result  in  material  being  thrown 
down  again  into  the  boot,  thus  necessitating  rehoisting. 

The  feeding  chute  is  almost  always  built  too  low.  It  should 
be  so  located  that  the  material  will  be  fed  into  the  third  bucket 
from  the  bottom.  This  allows  the  overflow  to  be  caught 


Running  a  Plant  to  Capacity         203 

by  the  two  buckets  below,  and  does  away  with  tne  necessity 
of  the  buckets  digging  their  load  from  the  boot.  Making  the 
buckets  dig  their  load  from  an  enclosed  boot  should  always 
be  avoided,  as  it  invariably  results  in  an  unnecessary  con- 
sumption of  power,  the  ripping  off  of  buckets  and  torn  belts. 
It  is  the  author's  opinion  that  more  elevator  trouble  is  due 
to  this  fault  than  any  other.  Fig.  79  shows  an  elevator  of 
standard  design. 


The  bucket  belt  should  always  be  kept  tight,  and  should 
run  on  a  slatted  pulley  at  the  bottom.  A  slatted  pulley  will 
not  allow  clay  to  "build  up"  on  it  and  therefore  the  belt 
will  run  true  in  the  housing  instead  of  scraping  the  sides  and 
occasionally  stopping  thru  friction. 

"Digging  out"  the  boots  twice  a  day  will  eliminate  a  great 
deal  of  trouble,  especially  in  wet  weather  or  when  using 
damp  materials.  The  dust  becomes  packed  very  hard  under 
the  buckets  and  the  friction  on  them  gradually  increases 
until  they  stop.  On  many  plants  the  boot  is  never  thought 
of  until  the  elevator  chokes  and  even  then  only  enough 
is  dug  out  to  start  up  again.  By  having  a  man  thoroly  clean 
all  the  boots  each  noon  and  night,  a  vast  amount  of  time 
and  temper  will  be  saved. 


204     Clay  Plant  Construction  and,  Operation 

PUG-MILLS 

Up  to  very  recently  these  machines  were  built  entirely  too 
light  for  the  heavy  duty  required  of  many  of  them.  This 
has  now  been  remedied,  but  hundreds  of  plants  are  equipped 
with  pug-mills  which  are  light  and  troublesome.  As  a  gen- 
eral rule  the  trouble  is  to  be  found  in  the  gears  and  inter- 
mediate shaft.  Gear  trouble  can  be  remedied  by  replacing 
the  much  used  cast-iron  by  either  cast-  or  cut-steel.  When 
the  intermediate  shaft  often  breaks,  it  should  be  replaced 
by  one  of  larger  diameter,  or  if  that  is  impossible,  by  one 
made  of  special  steel.  In  any  case,  it  is  well  to  have  an 
extra  one  on  hand  with  keyways  cut  and  ready  .for  an  emer- 
gency. Most  pug-mills,  being  set  on  a  platform,  which  at  best 
is  not  a  good  machine  foundation,  are  subjected  to  consider- 
able vibration.  This  has  a  tendency  to  loosen  bolts  and  de- 
stroy bearings.  The  use  of  spring  washers  under  the  nuts  will 
reduce  the  bolt  trouble,  but  the  pug-mill  should  be  examined 
daily  to  prevent  accidents. 

BRICK  OR  TILE   MACHINES 

Machines  are  subject  to  break-downs  in  the  same  parts  as 
pug-mills.  The  shafting  is  generally  the  most  troublesome, 
with  the  intermediate  easily  in  the  lead.  Many  clayworkers 
have  overcome  the  difficulty  by  installing  larger  shafts  all 
around.  Where  this  is  impossible  without  practically  re- 
building the  machine,  special  steels  must  be  resorted  to,  or 
extras  kept  in  constant  readiness.  Where  the  intermediate 
shaft  is  the  only  one  giving  trouble  it  is  a  very  good  plan 
to  have  the  extra  equipped  with  a  set  of  gears.  It  can  then 
be  put  into  place  with  little  delay. 

Machines  should  always  be  equipped  with  steel  gears.  A 
cast-iron  gear  will  lose  a  tooth  without  giving  a  moment's 
warning,  while  a  steel  one  will  wear  the  teeth  to  a  feather 
edge  before  breaking. 

In  going  from  one  plant  to  another  it  is  surprising  to  note 
the  number  of  machines  in  use  with  cracked  and  patched 
barrels.  In  a  case  of  this  kind,  when  the  conditions  become 
so  bad  as  to  require  a  new  barrel,  it  is  poor  practice  to  order 
a  duplicate  of  the  old  one.  If  the  maker  will  not  make 
something  stronger,  call  in  a  pattern  maker  who  knows  his 
business  and  have  him  make  a  pattern  that  will  produce  a 
casting  which  will  stand  up  in  spite  of  poor  pugging. 

CUTTING  TABLES 

There  are  many  small  parts   about  a  cutting  table  which 


Running  a  Plant  to  Capacity         205 

should  always  be  kept  on  hand.  Break-downs  on  a  cutter 
are  generally  caused  by  wear,  which  should  be  readily  caught 
before  it  gives  serious  trouble.  As  soon  as  a  cutter  begins 
to  "act  up,"  the  trouble  should  be  located  and,  if  the  respon- 
sible part  shoivs  wear,  it  should  be  replaced.  Patching  up 
does  not  pay,  as  a  general  rule,  with  automatic  cutters. 

KEY  TROUBLES 

One  of  the  most  annoying  of  the  little  troubles  on  a 
plant  is  caused  by  ill  fitting  keys.  A  pulley  or  a  gear  will 
constantly  slip  sideways,  probably  not  causing  any  great  loss 
of  time,  but  helping  to  keep  down  "capacity."  As  a  rule  it 
does  not  require  much  time  or  work  to  correct  this,  but 
there  can  be  no  question  that  on  some  plants  it  is  neglected. 
Day  after  day  the  plant  is  shut  down  for  five  or  ten  minutes 
at  a  time,  while  a  pulley  or  gear  is  driven  back  to  place,  and 
still  nothing  is  done  to  permanently  correct  the  trouble. 

A  key  once  properly  fitted  is  there,  and  it  is  worth  while 
to  see  that  this  item  is  properly  attended  to. 

BELT  TROUBLES 

When  this  subject  is  mentioned,  the  average  clay  worker  is 
"right  at  home," — and  there's  a  reason.  Briefly,  it  is  cheap 
belts.  The  author  has  sometimes  thot  that  if  it  were  not 
for  the  clay  plants  and  saw  mills,  most  of  the  companies 
making  cheap  belts  would  either  go  out  of  business  or  im- 
prove their  product.  The  amount  of  money  clay  workers  lose 
thru  shut-downs  to  take  up  belts,  repair  broken  lacings  and 
thru  "slipping,"  is  appalling.  In  every  instance  where  seri- 
ous trouble  of  this  kind  is  encountered  it  can  be  traced  to 
low  grade  belts,  or  belts  too  light  for  the  service.  The 
trouble  is  always  at  its  worst  during  a  rainy  spell,  when  the 
belts  draw  up  or  shrink,  and  tear  out  at  the  lacing.  After  a 
wet  spell  they  stretch  and  require  taking  up. 

To  constantly  go  thru  this  annoying  and  costly  experi- 
ence is  not  at  all  necessary.  It  is  not  the  intention  of  the 
writer  to  recommend  any  particular  make  of  belts,  but  a  plant 
can  be  equipped  so  that  this  trouble  is  reduced  to  a  minimum 
or  practically  eliminated.  The  best  of  belts  will  stretch  or  oc- 
casionally break  a  fastening,  but  invariably  they  give  sufficient 
warning  to  allow  repairs  to  be  made  out  of  operating  hours. 

Machines  are  often  equipped  with  belts  that  are  too  light 
(too  few  plies)  or  too  narrow.  Contact  between  the  belt  and 
the  pulley  is  the  all  important  factor  in  a  belt  drive  and  the 
greater  the  contact  the  better  the  drive.  Naturally,  drives 


206     Clay  Plant  Construction  and  Operation 

should  always  be  arranged  so  that  the  tight  side  of  the  belt 
is  on  the  bottom.  This  gives  a  greater  arc  of  contact  and 
eliminates  the  necessity  of  keeping  the  belt  too  tight.  This  in 
turn  eliminates  stretching  and  torn  joints.  When  the  drive  is 
wrong — the  tight  side  on  top — it  is  always  a  good  plan  to  add 
at  least  two  plies  to  the  thickness,  over  and  above  what  the 
tables  call  for. 

When  buying  belts  for  a  plant,  the  best — and  in  belts  this 
means  the  highest  priced — are  none  too  good,  no  matter 
whether  they  be  stitched  canvas,  woven  canvas,  rubber  or 
balata.  There  are  many  plants  which  are  only  prevented 
from  getting  "capacity"  thru  belt  troubles,  and  it  would  pay 
exceedingly  well  to  re-equip  thruout. 

Belts  should  not  be  allowed  to  run  until  they  slip,  but  as 
soon  as  they  show  signs  of  being  too  loose,  should  be  taken 
up.  When  a  joint  shows  signs  of  failing,  repair  it  as  soon 
as  the  plant  shuts  down. 

DRYERS 

On  many  plants  the  dryer  controls  the  "capacity."  Any 
interference  in  its  operation,  therefore,  tends  to  reduce  this 
capacity.  Mechanical  dryer  troubles  are  generally  limited  to 
the  tracks  and  cars,  and  in  waste-heat  dryers  to  the  fan  unit 
Tracks  should  be  so  securely  fastened  that  they  cannot  get 
out  of  gauge  and  they  should  be  kept  clean. 

The  bearings  of  the  cars  should  be  kept  in  good  condition 
and  should  be  oiled  every  time  they  come  thru.  The  author 
has  seen  plants — several  of  them — where  it  was  necessary 
to  shut  down  the  factory  several  times  each  day  so  that  the 
hands  could  go  into  the  tunnels  to  push  the  cars  down. 
The  trouble  was  wholly  in  the  tracks  and  car  bearings. 
The  loss  on  these  plants  ran  into  a  considerable  amount  in 
the  course  of  a  year,  and  there  are  many  like  them. 

The  fan  unit,  running  as  it  does  twenty-four  hours  a 
day  and  during  the  whole  year  or  season,  requires  most  care- 
ful attention.  This  is  especially  true  of  the  engine  and  fan 
bearings. 

KILNS 

It  is  a  very  usual  thing  for  plants  to  be  short  of  kiln  room. 
On  such  plants  it  is  not  unusual  for  the  output  to  be  inter- 
rupted thru  a  kiln  running  a  day  or  two  over  the  usual  burn- 
ing time.  As  a  rule,  there  is  little  excuse  for  this.  The 
trouble  can  generally  be  traced  to  sleepy  firemen,  unintelligent 
cleaning  and  firing,  or  dirty  kilns. 

It  is  necessary  to  closely  watch  the  kiln  department  at  all 


Running  a  Plant  to  Capacity         207 

times.  The  coal  should  be  closely  watched  to  see  that  a  bad 
car  is  not  at  times  "slipped  over,"  and  if  the  firemen  are 
likely  to  be  lax  it  may  be  good  policy  to  put  them  on  a  bonus 
system,  whereby  they  get  so  much  money  for  each  day  saved 
under  a  stated  period,  with  certain  deductions  for  spoiled 
ware. 

Much  kiln  trouble  is  due  to  dirty  bottoms.  Sometimes  a 
bottom  is  allowed  to  go  until  it  takes  from  one  to  three  days 
longer  to  make  the  burn,  and  unfortunately  this  extra  time 
is  on  the  hot  end,  when  the  kiln  is  simply  "eating  up"  fuel. 
Even  some  very  good  plant  operators  do  not  seem  to  grasp 
the  importance  of  clean  flues  and  when  designing  the  kiln 
make  no  allowance  for  the  accumulation  of  some  dirt  in 
the  kiln  bottoms. 

Keeping  the  temperature  constantly  progressing  during  a 
burn,  and  keeping  the  bottoms  clean,  will  aid  materially  in 
getting  capacity  where  "kiln  room"  is  an  important  factor. 

PLANT   INSPECTION 

Before  closing  the  chapter  the  author  wishes  to  make  a 
suggestion  to  clayworkers  which,  if  followed  out  regularly, 
will  prove  an  almost  certain  "trouble  preventive" : 

On  a  stated  day  each  week  while  the  plant  is  in  full  opera- 
tion, have  the  superintendent,  accompanied  by  the  master  me- 
chanic, machinist,  or  "handy  man,"  proceed  to  the  clay  bank  or 
pit.  There  they  pick  up  the  bank  foreman  and  together  very 
minutely  go  over  every  piece  of  equipment  that  can  in  any  way 
get  out  of  order.  Note  is  made  by  the  superintendent  of  every 
defective  or  worn  part  and  any  other  item  that  may  need 
attention  or  is  likely  to  interfere  with  operation. 

The  first  two  then  proceed  to  the  factory  and  with  the  fac- 
tory foreman  go  thru  the  same  process  in  this  department. 
Each  department  is  visited  in  the  same  way  until  the  entire 
plant  is  gone  over  A  copy  of  the  notes  taken  is  then  made 
out  for  each  foreman,  detailing  the  defects  found  in  his  de- 
partment, and  a  complete  list  is  made  out  for  the  master 
mechanic  or  repair  man.  Instructions  are  given  that  repairs 
and  changes  be  made  before  the  next  inspection. 

The  length  of  the  list  on  the  first  inspection  will  be  a 
surprise — even  on  the  best  of  plants — but  each  week  these 
lists  will  grow  smaller  and  the  number  of  jobs  become  fewer. 
The  effects  of  such  an  inspection  are  several.  The  super- 
intendent will  come  to  know  his  plant  as  he  never  knew  it 
before,  and  if  the  foremen  are  made  of  the  right  material, 


208     Clay  Plant  Construction  and  Operation 

they  will  take  pride  in  keeping  their  departments  in  such 
shape  that  no  list  is  given  them. 

But  most  important  is  the  fact  that  such  inspections,  if 
kept  up  regularly,  will  prevent  dozens  of  break-downs,  to 
say  nothing  of  small  repairs,  by  catching  defects  before  they 
give  trouble.  Such  inspections  need  not  be  confined  to  big 
plants,  for  even  where  the  owner  is  superintendent,  mechanic, 
head  burner  and  all  the  rest,  he  will  find  them  to  be  worth 
considerable  money  to  him. 

The  mere  fact  that  a  man  is  "around"  a  plant  continually 
is  not  enough.  It  requires  a  systematic  search  for  trouble 
causes  in  order  to  systematically  avoid  trouble. 


INDEX 


Accumulation  of  ware  in  dryer....  53 

Alloy  steel  augers 28 

Ang-le  of  die  opening 22,  38 

Arches   61,  137 

Arch  for  flues 127 

Arches  for  furnaces 103 

Arch  blocks 137 

Auger  v— -  17 

Auger  construction  27 

Auger  machine   18 

Auger  metal  28 

Auger  wear 28 

Backing  heat 160,  180 

Baffles  28 

Baffles  for  dies 34,  36 

Bag  walls 103 

Bands  for  crowns 96 

Battered  end  walls 123 

Batter  wall  backing 109 

Bearings  197 

Belt  speed 202 

Belt  troubles 205,  106 

Blast  pipe  connection 146 

Blowers  146 

Bottoms  of  kilns 83 

Brace  walls 115 

Brace  wall  construction 113 

Bracing 97 

Bracing  of  continuous  kiln 122 

Bracing  the  crowns 138 

Break  downs 191 

Brick  machines 17,  204 

Bridge  cracks 37 

Bridges  of  dies 33,  34 

Buckets  201 

Bucket  belts  203 

Building  crowns 100 

Building  plant 188 

Burning  coal  fired  continuous 

kiln  160 

Burning  equipment 184,  185 

Burning  out  deposits 171 

Burning  procedure  of  gas  kiln 

175,  176 

Burning  rules  for  gas-fired  kiln..!66 
Bushings  201 

Cage  for  haulage  system 195 

Canadian  clays 26 

Capacity  189 

Capacity  of  plant 183 

Carbonaceous  shales 80 

Care  of  motors 196,  197 

Caring  for  pan  step 199 

Cars  for  clay  pit 194 

Car  supply 7 

Chambers  under  fire 180 

Changing  plant  site 1 

Charging  room  floor 148 

Checking  samples 13 

Chemical   analysis 13 

Chimney  for  continuous  kiln 

141,    142 

Choice  of  equipment 184 

Chutes  ...„ 202 


Clay    pit 194 

Clay  testing 1-15 

Clean  out  floor 146,  148 

Cleaning  motors 197 

Cleaning  producer 170,  171 

Clinker   167 

Clutch  200,  201 

Coal  for  plant 207 

Coal  for  producers 149 

Coal  handling  for  producers 148 

Coal  required  for  producer  work.,166 

Coal  used  in  continuous  kilns 152 

Column  speed  22 

Comparison  of  augers 27 

Comparison,    European    and 

American  kilns 105 

Comparison    of    fan    and    chim- 
ney .., 141,  142 

Comparison  of  fuel  consumption..  46 

Concrete  walls  for  dryers 45 

Construction  of  kiln 79 

Construction  of  plant 188 

Continuous  kiln  construction 150 

Continuous  kiln  type 107 

Contract  work  on  kilns 188 

Controlling  gas  176 

Covering  of  kiln  crown 140 

Converting  brick  machine 16 

Conveyor  belts 196 

Cool  spot  67 

Cooling  tracks  for  dryer 58 

Cores   23 

Cost  of  die 38 

Cost  of  continuous  kiln 107 

Cost  of  drying 41 

Cost  of  insulation 92,  93,  94 

Cost     of    insulating     continuous 

kiln   120,  121 

Cost  of  kilns 81 

Couplings 195 

Cracks  due  to  bridge 37 

Cracked  ware 19 

Cracking  of  gas 169 

Cracking  hollow  ware 30 

Cross-over  flues 123,  124,  134 

Crown  of  continuous  kiln 135 

Crown  bands 96 

Crown  for  kiln 97 

Crown  wheels 201 

Crowns  of  kilns 91 

Cutting  tables  204 

Dampers  for  kilns 88 

Dead  air  space  of  kiln  wall 93 

Dead  bottom  kiln 83 

Deposit,  railroad  4 

Deposit  of  fire  clay 3 

Depth  of  fire  boxes 94 

Depreciation  of  kiln 184 

Design  of  auger  for  hollow  ware..  27' 

Design  of  dryers 41 

Determining  size  of  producer 149 

Determining  point  of  no  draft 163 

Development  of  dies 17 

Diameter  of  shaft 192 

Diamond  drill  11 

209 


210 


Index 


Dies 16-39 

Die  development  17 

Die  troubles    19 

Die  wear 37 

Difference  of  machines 18 

Direct  heat  dryer 185 

Distance  of  auger  from  die 30 

i  Distribution  of  metal  in  dies 32 

Doors  for  dryers 53,  54 

Double  track  tunnel 58 

Draft 161,  162 

Draft  flues  134 

Draft  gauge 146 

Draft  in  gas  kiln 177 

Draft  for  continuous  kiln 141,  142 

Drainage    5 

Drainage  for  dryer 46 

Drainage  for  kilns 81 

Drainage   of  continuous  kiln  .    . 

109,  110.  Ill 

Drawing  your   plant 186 

Drills  . 10,   11,  12 

Drilling   9,  10 

Drilling  of  crown 140 

Dryers    40-64,  20'5 

Dryer  buildings  43 

Dryer  cars  206 

Dryer  loss  25 

58 

3 

.184.   185 

25,  30 

48 

....198 


Dryer  tunnels  .. 
Drying,  clay  fails  to  dry 

Drying  equipment  

Drying  hollow  ware 

Drying  in  second  story.. 
Dry  pan  


Effect  of  raw  material  ................  23,  24 

Effect  of  setting  on  burning  ..........  66 

Efficiency  of  down  draft  kilns.... 

..........................................................  91.    92 

Efficiency  of  kiln  ................................  79 

Efflorescence    ......................................  173 

Elbow  flues  ..........................................  133 

Elevators  ..............................................  201 

Empty  chamber  in  gas  kiln  ........  175 

End  walls  ....................................  122,  123 

Expansion  joints  and  crowns  ........  136 

Expansion   joints  .............................  101 

Expansion  joints  of  continuous 

kiln  ......................................................  115 

Expansion  joints  in  cross-overs.  .134 
Exoansion  of  metallic  flues  ..........  132 

Extension  range  ................................  30 


Face  brick  from  up-draft  kilns.... 

...........................................................  .. 

Factory  built  without  thoro  tf^sts 
Fan  for  continuous  kiln  ...........  141. 

Fan  unit  ................................................ 

Filling  for  walls  ........................  116. 

Filling  tops  of  crown  ........................ 

Finding  weak   points  ........................ 

Fine  grinding  ................................  , 

Fineness  of  grain  ................................ 

Fire  clay  ................................................ 

Fire   clay  deposit  ................................ 

Fire   shafts   .......................................... 

Firing  period  length  ......................... 

Flashed  brick  setting 
Flashed  ware  in  gas  kiln  .......  : 

Flat  die  ............................................  20, 

Flow  of  clay 

Flue  construction  ........... 

............................  125.  126.  127,  128. 

Flue  system  of  kiln 
Follow  board  ............................. 

Force  feed 
Foundation 
Foundation  of  kilns  ..................  81, 


64 
2 

142 
206 
H7 
1?9 
1P1 
24 
24 
13 
3 

15r> 
180 
77 
178 
21 
19 

129 
83 
62 
31 
204 
108 


Friction  in  barrel 28 

Furnaces    101 

Gas  flues  :.129,  148 

Gas  manufacture  166,  167,  168 

Gas  producers  149 

Gas  temperature  168 

Gas  tight  joints  125,  126 

Gears  193 

Gear  trouble  204 

Geology  5 

Glacial  areas   9 

Grade  of  dryer  tracks 51 

Grate  area  for  kiln 87 

Grog  25 

Grooving  of  ware  35 

Guide  for  locating  flues 154 

Hand  auger  drill 10 

Harmony  among  employes 191 

Haulage  system 195 

Head  pulleys 201 

Height    of    setting 68 

Height  of  stack  for  kiln 87 

Herring  bone  setting 66 

Hillside  bank  5 

Hip  roof  design 1 143 

Hollow  tile  for  dryers 46 

Hollow  ware  warps 30 

Hollow  ware  cracks  30 

Hollow  ware  drying  30 

Hollow  wrfre  on  brick  machines..  18 

Hooks    195 

Hoppers  for  producers 148 

Hot  spot   67,     90 

Human  force  feed  32 

Incline 194,  195 

Increasing   capacity    of  gas   kiln 

176 

Inner  section  wall     118 

Ironing  kilns  97 

Inspection     of     continuous     kiln 

construction  149,  150 

Inspection  of  plant  207 

Insulated  wall  119,  120.  121 

Insulation  of  kilns 91,  92,  93,     94 


Key  for  erown 
Key  troubles  ... 

Kilns  

Kiln  building  . 

Kiln  design  

Kinds   of   dies 
Knife  holders  . 


100 

205 

.79-150,  200 

79 

66 

20 
....192 


Labor  in  setting  68 

Labor  on  plant  191 

Land  to  be  produced  182 

Land  slides  9 

Laying  common  brick  95 

Laying  out  the  plant 186 

Letting   construction    work 107 

Light    conditions    187 

Limestone  for  drying 25 

Liners  of  .barrel  20 

Lining  of  continuous  kiln 114 

Lining  of  kiln  crowns 97 

Lining  dies 39 

Lip  of  auger  30 

Location  of  drill  holes 10,  14 

Location  of  plant  1,  2,  3,     6 

Long  burning    period ...  80 

Losses  due  to  sampling 2,     9 

Machine  equipment  183 

Machinery  requirements  190 

Manner  of  feeding  fuel  160 

Market    .  6 


Index 


211 


Material  for  hollow  ware 25.  26 

Mechanical  dryer  185 

Metal  baffles 36 

Metal  distribution  in  dies 32 

Method  of  laying  out  plant 186 

Methods  of  setting- 

74,    75,  76,   77,   78,    156 

Moisture  in  flue  system..... 47 

Money  spent  in  drilling 

Mortar  for  continuous  kilns. .113,  114 
Mortar  for  continuous  kiln  crown 

135 

Mortar" for  inner  wall 118,  120 

Mortar  in  kiln  masonry 95 

Motors   196,   197 

Mouth  of  dies 22 

Multiple  stacks   ..  -.87,  88 

Necessitating        of       systematic 

sampling 8 

Need  for  testing  property 1 

"No  draft"  point 162,   16?, 

Non-caking  flue 155 

Normal  operating  conditions  for 

kiln  151 

Number     of     chambers     carried 

176,    177 

Number  of  sections  in  circuit 163 

Number  of  sections  to  fire 159 

Object  of  dryers  41 

Oiling  pan  step  ... 
Open  air  dryers  ... 

Open  cut  

Origin    of    American    continuous 

kilns  104 

Origin  of  die  troubles 

Overburden  

Paper  partitions  157 

Pinions   201 

Pitch  of  auger  1' 

Plant  buildings  18I 

Plant    inspection    207 

Pokering  producer  167 

Polish  of  auger  28,   29 

Position  of  flues  127,  128 

Power    considerations    ....187 

Power  consumption  

Power  plant   196 

Property  testing  9,  12 

Practical  tests  12 

Premature     paper     partition     in 

burning  159 

Pressure  in  auger  machine 28 

Preventing  dust   199 

Producers    146 

Producer  gas  fired  kilns 165 

Producer  gas  house 145,  146 

Pug  mill  31,  204 

Pug  mill  shaft  breaks 192 

Pull  of  the  fires 71 

Purchasing  belts  ...  -.206 

Race  flues  %. 154 

Rack   dryers   42,  43 

Radiation    dryers    44,  45 

Radiation    from    kiln    walls 91,  92 

Rails  for  dryer : 50,  51 

Rails  for  clay  pit 194 

Railroad  built  to  deposit 4 

Railroad    service    7 

Rate  of  fire   travel 162 

Rate  of  firing  producer  167 

Raw  material  storage 184 

Raw  materials  and   dies 23,  24 

Refractory  clays  13 


Relation  of  grate  and  stack  area..  87 
Relation   of   grate    area   to    floor 

area 101,  102 

Repair  list  207 

Repair  parts  193 

Resistance  to  flow 19 

Ring  setting  73 

Rollers  for  expansion 132 

Roof  construction  142,  143 

Roof  of  dryer  48 

Roof  for  storage  tracks 60 

Runner  brick  73 

Salt  for  drying 25 

Sampling   clay    8,     9 

Sagging  of  heads  71 

Saw-tooth   bridge   37,  38 

Scorers  and  scratchers 35 

Scrapers  198 

Screen   plates  and   dies 25 

Screen   plates 198,  199 

Sections   under  fire 159 

Selecting  a  burning  system 185 

Selection  of  clay  property 4 

Setting  at  bag  wall 71 

Setting  benches 156 

Setting  effect  68 

Setting  affected  by  rough  texture 

brick  66 

Setting  gas-fired  kilns. ...171,  172,  173 

Setting  methods 74,  75,  76,  77,     78 

Setting  tight  bolt 61 

Setting  ware  in  continuous  kilns. .152 

Setting  of   kiln 108 

Shale  pit , 194 

Shortening  burning  periods 80 

Short  cutting  of  gases 87 

Side  walls  of  chamber  kiln 119 

Single  track  tunnel 58 

Size   of  barrel 31 

Size  of  flue 155 

Shafts   193 

Shaft  location  18,  19 

Shipping    facilities    ".     7 

Skintle  brick,  setting 66 

Slack   for  continuous   kilns 152 

Slipping  of  belts 206 

Soft   bottoms    154 

Solid  bottom  kiln 83 

Solid  brick  wall 117 

Soot    176 

Space  around  an  auger 30 

Space  between  die  and  auger 31 

Space  over  ware  in  dryer 51 

Special  flues  for  watersmoking....!57 

Sneed  due  to  taper 22 

Speed  of  augers 27 

Speed  of  auger  machine  19,  20 

Speed  of  column 22 

Spreaders  23 

Spring  of  crown 98 

Stack  for  dryer 55,  56 

Stacks  for  kiln 85.   86,  87 

Stack  dies  22 

Starting  crowns  98 

Starting  gas  kiln 174 

Steam  pressure  at  blower 168 

Steel  shell  kilns  96 

Step  for  dry  pan 199 

Steam  gauge   146 

Steam  shovel  operation 5 

Storage  shed  196 

Storage  tracks  for  dryer 58 

Superintendent  of  plant 207 

Supervision  of  pit 194 

Supervision  of  testing 13 

Supply  of  repair  parts 193 

Support  of  crown 99 

Surface  clays  of  Canada 26 


212 


Index 


Surface  samples  28 

Switching  charges 1 

Tar  176 

Taper  of  brick  machine 17 

Taper  of  die 21,  22,  23 

Tapered  die 20,  21,  22,  23 

Temperature   control  207 

Tempering  71,  73 

Tempering  water  8 

Testing  clay  13,  15 

Testing  properties  *> 

Testing  samples   8,  12 

Tight  bolt  setting 61,  76 

Tile  machines 204 

Tongue  and  groove  brick 126,  130 

Tool  steel  drill 12 

Topography 

Tracks  in  dryer  53 

Tracks  in  pit  

Trusses  for  roof 

Tunnel  design  53 

Tunnel  dimensions 51,  52 

Tunnels   for  dryer 58 

Types  of  dies 20 

Types  of  dryers  

Unbalanced  die  28 

Underground  flues  135 

Unflashed   setting 76 

Unloaders   in   continuous   kiln 163 

Up-take  flues  132,  133 


Vent  stack  construction 55,  56 

Wall     construction     for     tunnel 

kilns  112 

Wall  for  dryer 44,  45,  46 

Walls  of  kilns  90 

Ware  adapted  to  tunnel  kilns 153 

Ware  could  not  be  dried 5 

Ware  manufactured 6 

Ware  to  be  produced 182 

Warping  of  hollow  ware 30 

Waste  heat  dryer 184,  185 

Waste  heat  flues 47 

Waste  steam  dryer  185 

Watersmoking    173 

Watersmoking  difficulties  70 

Watersmoking  flues  130 

Watersmoking  in  gas  kilns 

172,    1713,  174 

Watersmoking    in    tunnel     kilns 

157,  158 

Water  supply  7 

Wear  of  crowns  138 

Weathering  8 

Weathered  clay  „. 

Weather   protector   42 

Weights  of  die  24,  35 

Welding  qualities  of  clay 37 

Well  drill  

Wicket  damper  89 

Wicket  fires  158,  161 


BOOK 
INCREASE  TO 

D"AY    AND    TO 
OVERDUE. 


- 


LD21_10»-5,'43(6061S) 


ii  : 


ilh 


